[pstl] Fix comparison function passed to std::inplace_merge

[jwakely]

This needs to be an ordering, not an equality comparison.

Fixes #80217

[github-actions]

⚠️ C/C++ code formatter, clang-format found issues in your code. ⚠️

You can test this locally with the following command:

git-clang-format --diff 1bbb797e9c7f37aa814b9bbaba2961f730a26891 86390895753fc7d914cfee02a6b8331cc3dfcbfe -- pstl/test/std/algorithms/alg.merge/inplace_merge.pass.cpp

View the diff from clang-format here.

diff --git a/pstl/test/std/algorithms/alg.merge/inplace_merge.pass.cpp b/pstl/test/std/algorithms/alg.merge/inplace_merge.pass.cpp
index 4d706f067b..24b210e3fa 100644
--- a/pstl/test/std/algorithms/alg.merge/inplace_merge.pass.cpp
+++ b/pstl/test/std/algorithms/alg.merge/inplace_merge.pass.cpp
@@ -147,10 +147,10 @@ main()
 
     test_algo_basic_single<int32_t>(run_for_rnd_bi<test_non_const<int32_t>>());
 
-    test_by_type<MemoryChecker>(
-        [](std::size_t idx){ return MemoryChecker{std::int32_t(idx * 2)}; },
-        [](std::size_t idx){ return MemoryChecker{std::int32_t(idx * 2 + 1)}; },
-        [](const MemoryChecker& val1, const MemoryChecker& val2){ return val1.value() < val2.value(); });
+    test_by_type<MemoryChecker>([](std::size_t idx) { return MemoryChecker{std::int32_t(idx * 2)}; },
+                                [](std::size_t idx) { return MemoryChecker{std::int32_t(idx * 2 + 1)}; },
+                                [](const MemoryChecker& val1, const MemoryChecker& val2)
+                                { return val1.value() < val2.value(); });
     EXPECT_FALSE(MemoryChecker::alive_objects() < 0, "wrong effect from inplace_merge: number of ctors calls < num of dtors calls");
     EXPECT_FALSE(MemoryChecker::alive_objects() > 0, "wrong effect from inplace_merge: number of ctors calls > num of dtors calls");
 

[jwakely]

⚠️ C/C++ code formatter, clang-format found issues in your code. ⚠️

I preserved the original formatting, which is locally consistent with the pstl/test/* style. If somebody wants to change that it should be done to the whole file, not just the lines I'm fixing.