fix(c): remove protection against reloading

It's only for plugin configuration files

nvim/ftplugin/c.lua

@@ -1,8 +1,3 @@
-if vim.g.did_load_c_plugin then
-  return
-end
-vim.g.did_load_c_plugin = true
-
 -- Exit if the language server isn't available
 if vim.fn.executable('clangd') ~= 1 then
   return