Fix gcc compilation warning in test case [NFC]

Without this, gcc (7.4) complains with

../tools/clang/tools/extra/clangd/unittests/PrintASTTests.cpp:99:28: error: ISO C++11 requires at least one argument for the "..." in a variadic macro [-Werror]
                         })));
                            ^

llvm-svn: 360334

clang-tools-extra/clangd/unittests/PrintASTTests.cpp

@@ -96,7 +96,7 @@ INSTANTIATE_TEST_CASE_P(ASTUtilsTests, ASTUtils,
                                   struct Bar { friend class Foo<int>; };
                                   template <> struct ^Foo<int> {};)cpp",
                                 {"<int>"}},
-                        })));
+                        })),);
 } // namespace
 } // namespace clangd
 } // namespace clang