[gn build] update two comments

upstream-commit: 6121122

Author: nico

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

@@ -8,7 +8,7 @@ source_set("remote") {
   sources = []
   if (false) {
     sources += [
-      # FIXME comment
+      # Make `gn format` not collapse this, for sync_source_lists_from_cmake.py.
       "Client.cpp",
     ]
   }

llvm/utils/gn/secondary/clang-tools-extra/clangd/index/remote/unimplemented/BUILD.gn

@@ -6,7 +6,7 @@ source_set("unimplemented") {
   ]
   include_dirs = [ "../../.." ]
   sources = [
-    # FIXME comment
+    # Make `gn format` not collapse this, for sync_source_lists_from_cmake.py.
     "UnimplementedClient.cpp",
   ]
 }