[clangd][test] Account for downstream coroutines hack in isKeywords test

Author: jrtc27

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

@@ -808,6 +808,10 @@ TEST(SourceCodeTests, isKeywords) {
   LangOpts.Coroutines = true;
   EXPECT_TRUE(isKeyword("int", LangOpts));
   EXPECT_TRUE(isKeyword("return", LangOpts));
+  // CHERI-TODO: COROUTINES_KEYWORD is not included in CXX20_KEYWORD until
+  // https://github.com/CTSRD-CHERI/llvm-project/issues/717 has been fixed.
+  EXPECT_FALSE(isKeyword("co_await", LangOpts));
+  LangOpts.Coroutines = true;
   EXPECT_TRUE(isKeyword("co_await", LangOpts));
 
   // these are identifiers (not keywords!) with special meaning in some