[NFC] remove duplciated unittests for modules

There was an overlook to duplicate the unittests for modules. This patch
removes one of this duplication.

Author: ChuanqiXu9

clang/unittests/AST/DeclTest.cpp

@@ -240,23 +240,6 @@ TEST(Decl, ModuleAndInternalLinkage) {
 
   EXPECT_EQ(b->getFormalLinkage(), ModuleLinkage);
   EXPECT_EQ(g->getFormalLinkage(), ModuleLinkage);
-
-  AST = tooling::buildASTFromCodeWithArgs(
-      Code.code(), /*Args=*/{"-std=c++20"});
-  ASTContext &CtxTS = AST->getASTContext();
-  a = selectFirst<VarDecl>("a", match(varDecl(hasName("a")).bind("a"), CtxTS));
-  f = selectFirst<FunctionDecl>(
-      "f", match(functionDecl(hasName("f")).bind("f"), CtxTS));
-
-  EXPECT_EQ(a->getFormalLinkage(), InternalLinkage);
-  EXPECT_EQ(f->getFormalLinkage(), InternalLinkage);
-
-  b = selectFirst<VarDecl>("b", match(varDecl(hasName("b")).bind("b"), CtxTS));
-  g = selectFirst<FunctionDecl>(
-      "g", match(functionDecl(hasName("g")).bind("g"), CtxTS));
-
-  EXPECT_EQ(b->getFormalLinkage(), ModuleLinkage);
-  EXPECT_EQ(g->getFormalLinkage(), ModuleLinkage);
 }
 
 TEST(Decl, GetNonTransparentDeclContext) {