[llvm] [NFC] LLVM reduce: remove unused variable (PR #133584)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `llvm-clang-x86_64-expensive-checks-debian` running on `gribozavr4` while building `llvm` at step 5 "build-unified-tree".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/16/builds/16464

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 5 (build-unified-tree) failure: build (failure)
...
52.618 [4/23/4091] Linking CXX executable bin/sancov
52.623 [4/22/4092] Linking CXX executable bin/llvm-debuginfo-analyzer
52.657 [4/21/4093] Linking CXX executable bin/llvm-cfi-verify
52.715 [4/20/4094] Linking CXX executable bin/llvm-lipo
52.733 [4/19/4095] Linking CXX executable bin/llvm-profgen
52.785 [4/18/4096] Linking CXX executable bin/llvm-libtool-darwin
52.966 [4/17/4097] Linking CXX executable bin/llvm-jitlink
54.577 [4/16/4098] Linking CXX executable bin/dsymutil
54.677 [4/15/4099] Linking CXX executable bin/llvm-split
54.706 [4/14/4100] Building CXX object tools/llvm-reduce/CMakeFiles/llvm-reduce.dir/deltas/ReduceOperandsToArgs.cpp.o
FAILED: tools/llvm-reduce/CMakeFiles/llvm-reduce.dir/deltas/ReduceOperandsToArgs.cpp.o 
CCACHE_CPP2=yes CCACHE_HASHDIR=yes /usr/bin/ccache /usr/bin/clang++ -DEXPENSIVE_CHECKS -DGTEST_HAS_RTTI=0 -DLLVM_BUILD_STATIC -D_DEBUG -D_GLIBCXX_ASSERTIONS -D_GLIBCXX_DEBUG -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/b/1/llvm-clang-x86_64-expensive-checks-debian/build/tools/llvm-reduce -I/b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/llvm/tools/llvm-reduce -I/b/1/llvm-clang-x86_64-expensive-checks-debian/build/include -I/b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/llvm/include -U_GLIBCXX_DEBUG -fPIC -fvisibility-inlines-hidden -Werror=date-time -Werror=unguarded-availability-new -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -pedantic -Wno-long-long -Wc++98-compat-extra-semi -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wsuggest-override -Wstring-conversion -Wmisleading-indentation -Wctad-maybe-unsupported -fdiagnostics-color -ffunction-sections -fdata-sections -O3 -DNDEBUG  -fno-exceptions -funwind-tables -fno-rtti -UNDEBUG -std=c++17 -MD -MT tools/llvm-reduce/CMakeFiles/llvm-reduce.dir/deltas/ReduceOperandsToArgs.cpp.o -MF tools/llvm-reduce/CMakeFiles/llvm-reduce.dir/deltas/ReduceOperandsToArgs.cpp.o.d -o tools/llvm-reduce/CMakeFiles/llvm-reduce.dir/deltas/ReduceOperandsToArgs.cpp.o -c /b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/llvm/tools/llvm-reduce/deltas/ReduceOperandsToArgs.cpp
/b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/llvm/tools/llvm-reduce/deltas/ReduceOperandsToArgs.cpp:112:13: error: 'setFastMathFlags' is a private member of 'llvm::FPMathOperator'
      FPOp->setFastMathFlags(CI->getFastMathFlags());
            ^
/b/1/llvm-clang-x86_64-expensive-checks-debian/llvm-project/llvm/include/llvm/IR/Operator.h:264:8: note: declared private here
  void setFastMathFlags(FastMathFlags FMF) {
       ^
1 error generated.
54.713 [4/13/4101] Linking CXX executable bin/llvm-gsymutil
54.749 [4/12/4102] Linking CXX executable bin/llvm-dwarfutil
54.797 [4/11/4103] Linking CXX executable bin/llvm-c-test
54.844 [4/10/4104] Linking CXX executable bin/bugpoint
54.848 [4/9/4105] Linking CXX executable bin/llvm-dwp
54.878 [4/8/4106] Linking CXX executable bin/llvm-isel-fuzzer
54.917 [4/7/4107] Linking CXX executable bin/llc
54.933 [4/6/4108] Linking CXX executable bin/llvm-opt-fuzzer
55.026 [4/5/4109] Linking CXX executable bin/opt
55.109 [4/4/4110] Linking CXX executable bin/lld
55.215 [4/3/4111] Linking CXX executable bin/llvm-lto
55.325 [4/2/4112] Linking CXX executable bin/llvm-lto2
55.556 [4/1/4113] Linking CXX shared library lib/libLTO.so.21.0git
ninja: build stopped: subcommand failed.

```

</details>

https://github.com/llvm/llvm-project/pull/133584