[clang][test] mark tests added in ee8524087c as unsupported on AIX

These tests are failing on the PPC64 AIX CI bot, but it's unclear why,
as they pass on other CI jobs.
I marked them as unsupported on AIX for now while investigating the failure.

clang/test/Index/index-concept-kind.cpp

@@ -1,5 +1,5 @@
 // RUN: c-index-test -index-file %s -std=gnu++20 | FileCheck %s
-
+// UNSUPPORTED: aix
 template <typename T>
 concept LargeType = sizeof(T) > 8;
 // CHECK: [indexDeclaration]: kind: concept | name: LargeType | USR: c:@CT@LargeType | lang: C | cursor: ConceptDecl=LargeType:[[@LINE-1]]:9 (Definition) | loc: [[@LINE-1]]:9 | semantic-container: [TU] | lexical-container: [TU] | isRedecl: 0 | isDef: 1 | isContainer: 0 | isImplicit: 0

clang/test/Index/index-concepts.cpp

@@ -1,5 +1,5 @@
 // RUN: c-index-test -test-load-source all %s -std=gnu++20 -fno-delayed-template-parsing | FileCheck %s
-
+// UNSUPPORTED: aix
 template<class T>
 struct type_trait {
     const static bool value = false;