Fix gcc compilation warning in test case [NFC]
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]
                         })));
                            ^

git-svn-id: a34e9779ed74578ad5922b3306b3d80a0c825546@360334 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/clang-tools-extra,llvm-mirror/clang-tools-extra,llvm-mirror/clang-tools-extra,llvm-mirror/clang-tools-extra