fix(treesitter): use the right loading order for base queries (#20117)

Use the first, not last, query for a language on runtimepath. Typically,
this implies that a user query will override a site plugin query, which 
will override a bundled runtime query.

runtime/lua/vim/treesitter/query.lua

@@ -97,7 +97,7 @@ function M.get_query_files(lang, query_name, is_included)
 
     if extension then
       table.insert(extensions, filename)
-    else
+    elseif base_query == nil then
       base_query = filename
     end
     io.close(file)