[llvm] [YAML][NFC] precommit wrong test case (PR #131782)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `llvm-nvptx64-nvidia-ubuntu` running on `as-builder-7` while building `llvm` at step 6 "test-build-unified-tree-check-llvm".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/160/builds/15318

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

```
Step 6 (test-build-unified-tree-check-llvm) failure: test (failure)
...
0.965 [2/10/693] Linking CXX executable unittests/ExecutionEngine/Orc/OrcJITTests
0.969 [2/9/694] Linking CXX executable unittests/Transforms/Utils/UtilsTests
0.982 [2/8/695] Linking CXX executable unittests/Transforms/Vectorize/SandboxVectorizer/SandboxVectorizerTests
1.008 [2/7/696] Linking CXX executable unittests/tools/llvm-exegesis/LLVMExegesisTests
1.033 [2/6/697] Linking CXX executable unittests/CodeGen/CodeGenTests
1.057 [2/5/698] Linking CXX executable unittests/Frontend/LLVMFrontendTests
1.105 [2/4/699] Linking CXX executable unittests/Analysis/AnalysisTests
1.232 [2/3/700] Linking CXX executable unittests/IR/IRTests
1.396 [2/2/701] Linking CXX executable unittests/ADT/ADTTests
5.051 [2/1/702] Building CXX object unittests/Support/CMakeFiles/SupportTests.dir/YAMLIOTest.cpp.o
FAILED: unittests/Support/CMakeFiles/SupportTests.dir/YAMLIOTest.cpp.o 
CCACHE_CPP2=yes CCACHE_HASHDIR=yes /usr/bin/ccache /usr/bin/c++ -DGTEST_HAS_RTTI=0 -DLLVM_BUILD_STATIC -D_DEBUG -D_GLIBCXX_ASSERTIONS -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx64-nvidia-ubuntu/build/unittests/Support -I/home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx64-nvidia-ubuntu/llvm-project/llvm/unittests/Support -I/home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx64-nvidia-ubuntu/build/include -I/home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx64-nvidia-ubuntu/llvm-project/llvm/include -I/home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx64-nvidia-ubuntu/llvm-project/third-party/unittest/googletest/include -I/home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx64-nvidia-ubuntu/llvm-project/third-party/unittest/googlemock/include -fPIC -fno-semantic-interposition -fvisibility-inlines-hidden -Werror=date-time -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wno-missing-field-initializers -pedantic -Wno-long-long -Wimplicit-fallthrough -Wno-uninitialized -Wno-nonnull -Wno-class-memaccess -Wno-redundant-move -Wno-pessimizing-move -Wno-noexcept-type -Wdelete-non-virtual-dtor -Wsuggest-override -Wno-comment -Wno-misleading-indentation -Wctad-maybe-unsupported -fdiagnostics-color -ffunction-sections -fdata-sections -O3 -DNDEBUG  -Wno-dangling-else -Wno-variadic-macros -fno-exceptions -funwind-tables -fno-rtti -UNDEBUG -Wno-suggest-override -std=c++17 -MD -MT unittests/Support/CMakeFiles/SupportTests.dir/YAMLIOTest.cpp.o -MF unittests/Support/CMakeFiles/SupportTests.dir/YAMLIOTest.cpp.o.d -o unittests/Support/CMakeFiles/SupportTests.dir/YAMLIOTest.cpp.o -c /home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx64-nvidia-ubuntu/llvm-project/llvm/unittests/Support/YAMLIOTest.cpp
/home/buildbot/worker/as-builder-7/ramdisk/llvm-nvptx64-nvidia-ubuntu/llvm-project/llvm/unittests/Support/YAMLIOTest.cpp:1280:20: error: explicit specialization of ‘template<class T> struct llvm::yaml::MappingTraits’ outside its namespace must use a nested-name-specifier [-fpermissive]
 1280 | template <> struct MappingTraits<V> {
      |                    ^~~~~~~~~~~~~~~~
ninja: build stopped: subcommand failed.

```

</details>

https://github.com/llvm/llvm-project/pull/131782