Revert "[YAML] Make `std::array` available (#116059)"

Compilation failed on gcc hosts.

This reverts commit 941f704f0892317701fd263603a729e0ef86dda6.
(llvmorg-20-init-12117-g941f704f0892)
diff --git a/llvm/include/llvm/Support/YAMLTraits.h b/llvm/include/llvm/Support/YAMLTraits.h
index 510f76a..403584e 100644
--- a/llvm/include/llvm/Support/YAMLTraits.h
+++ b/llvm/include/llvm/Support/YAMLTraits.h
@@ -2007,11 +2007,6 @@
     : SequenceTraitsImpl<std::vector<T>, SequenceElementTraits<T>::flow> {};
 template <typename T, unsigned N>
 struct SequenceTraits<
-    std::array<T, N>,
-    std::enable_if_t<CheckIsBool<SequenceElementTraits<T>::flow>::value>>
-    : SequenceTraitsImpl<std::array<T, N>, SequenceElementTraits<T>::flow> {};
-template <typename T, unsigned N>
-struct SequenceTraits<
     SmallVector<T, N>,
     std::enable_if_t<CheckIsBool<SequenceElementTraits<T>::flow>::value>>
     : SequenceTraitsImpl<SmallVector<T, N>, SequenceElementTraits<T>::flow> {};
diff --git a/llvm/unittests/Support/YAMLIOTest.cpp b/llvm/unittests/Support/YAMLIOTest.cpp
index a7d1b33..2d76b15 100644
--- a/llvm/unittests/Support/YAMLIOTest.cpp
+++ b/llvm/unittests/Support/YAMLIOTest.cpp
@@ -3366,15 +3366,6 @@
   int values[4];
 };
 
-struct StdArray {
-  StdArray() {
-    // Initialize to int max as a sentinel value.
-    for (auto &v : values)
-      v = std::numeric_limits<int>::max();
-  }
-  std::array<int, 4> values;
-};
-
 namespace llvm {
 namespace yaml {
 template <> struct MappingTraits<FixedArray> {
@@ -3383,21 +3374,11 @@
     io.mapRequired("Values", array);
   }
 };
-template <> struct MappingTraits<StdArray> {
-  static void mapping(IO &io, StdArray &st) {
-    io.mapRequired("Values", st.values);
-  }
-};
 } // namespace yaml
 } // namespace llvm
 
-using TestTypes = ::testing::Types<FixedArray, StdArray>;
-
-template <typename T> class YAMLIO : public testing::Test {};
-TYPED_TEST_SUITE(YAMLIO, TestTypes, );
-
-TYPED_TEST(YAMLIO, FixedSizeArray) {
-  TypeParam faval;
+TEST(YAMLIO, FixedSizeArray) {
+  FixedArray faval;
   Input yin("---\nValues:  [ 1, 2, 3, 4 ]\n...\n");
   yin >> faval;
 
@@ -3419,9 +3400,9 @@
   ASSERT_EQ(serialized, expected);
 }
 
-TYPED_TEST(YAMLIO, FixedSizeArrayMismatch) {
+TEST(YAMLIO, FixedSizeArrayMismatch) {
   {
-    TypeParam faval;
+    FixedArray faval;
     Input yin("---\nValues:  [ 1, 2, 3 ]\n...\n");
     yin >> faval;
 
@@ -3434,7 +3415,7 @@
   }
 
   {
-    TypeParam faval;
+    FixedArray faval;
     Input yin("---\nValues:  [ 1, 2, 3, 4, 5 ]\n...\n");
     yin >> faval;