Automerge: [gn build] Port 2c4b876

Author: llvmgnsyncbot

llvm/utils/gn/secondary/clang-tools-extra/clangd/unittests/BUILD.gn

@@ -108,6 +108,7 @@ unittest("ClangdTests") {
     "SourceCodeTests.cpp",
     "StdLibTests.cpp",
     "SymbolCollectorTests.cpp",
+    "SymbolDocumentationTests.cpp",
     "SymbolInfoTests.cpp",
     "SyncAPI.cpp",
     "TUSchedulerTests.cpp",