[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-x86_64-debian-dylib` running on `gribozavr4` while building `llvm` at step 5 "build-unified-tree".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/60/builds/23382

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

```
Step 5 (build-unified-tree) failure: build (failure)
...
43.026 [1427/11/5807] Building CXX object unittests/Analysis/InlineAdvisorPlugin/CMakeFiles/InlineAdvisorPlugin.dir/InlineAdvisorPlugin.cpp.o
43.026 [1427/10/5808] Building CXX object unittests/Analysis/InlineOrderPlugin/CMakeFiles/InlineOrderPlugin.dir/InlineOrderPlugin.cpp.o
43.027 [1427/9/5809] Building CXX object unittests/Passes/Plugins/TestPlugin/CMakeFiles/TestPlugin.dir/TestPlugin.cpp.o
43.027 [1427/8/5810] Building CXX object unittests/Passes/Plugins/DoublerPlugin/CMakeFiles/DoublerPlugin.dir/DoublerPlugin.cpp.o
43.045 [1427/7/5811] Building CXX object tools/clang/tools/libclang/CMakeFiles/libclang.dir/CXIndexDataConsumer.cpp.o
43.105 [1427/6/5812] Building CXX object tools/clang/tools/libclang/CMakeFiles/libclang.dir/CIndex.cpp.o
43.122 [1427/5/5813] Building CXX object tools/clang/tools/libclang/CMakeFiles/libclang.dir/Indexing.cpp.o
43.200 [1427/4/5814] Building CXX object tools/clang/tools/libclang/CMakeFiles/libclang.dir/CXExtractAPI.cpp.o
43.282 [1427/3/5815] Building CXX object tools/lldb/tools/lldb-instr/CMakeFiles/lldb-instr.dir/Instrument.cpp.o
45.458 [1427/2/5816] 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++ -DGTEST_HAS_RTTI=0 -D_DEBUG -D_GLIBCXX_ASSERTIONS -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/b/1/llvm-x86_64-debian-dylib/build/tools/llvm-reduce -I/b/1/llvm-x86_64-debian-dylib/llvm-project/llvm/tools/llvm-reduce -I/b/1/llvm-x86_64-debian-dylib/build/include -I/b/1/llvm-x86_64-debian-dylib/llvm-project/llvm/include -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-x86_64-debian-dylib/llvm-project/llvm/tools/llvm-reduce/deltas/ReduceOperandsToArgs.cpp
/b/1/llvm-x86_64-debian-dylib/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-x86_64-debian-dylib/llvm-project/llvm/include/llvm/IR/Operator.h:264:8: note: declared private here
  void setFastMathFlags(FastMathFlags FMF) {
       ^
1 error generated.
47.188 [1427/1/5817] Linking CXX shared library lib/libLLVM.so.21.0git
ninja: build stopped: subcommand failed.

```

</details>

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