Rework coc-config

.config/nvim/coc-settings.json

 {
     "languageserver": {
-        "clangd": {
-            "command": "clangd",
-            "args": ["--background-index"],
-            "rootPatterns": ["compile_flags.txt", "compile_commands.json", ".git/", ".hg/"],
-            "filetypes": ["c", "cpp", "objc", "objcpp"]
-        },
         "ccls": {
             "command": "ccls",
             "filetypes": ["c", "cpp", "cuda", "objc", "objcpp"],
@@ -802,6 +796,7 @@
       "gfmul",
       "gpio",
       "gridlayout",
+      "gsettings",
       "gwstat",
       "hackmd",
       "hasharea",