chore(lsp): remove custom header switch mapping

lua/plugins/20-lsp.lua

@@ -3,15 +3,6 @@ return {
     "AstroNvim/astrolsp",
     ---@type AstroLSPOpts
     opts = {
-        mappings = {
-            n = {
-                gh = {
-                    function() require("clangd_extensions.switch_source_header").switch_source_header() end,
-                    desc = "Switch to matching source or header file",
-                    cond = "textDocument/switchSourceHeader",
-                },
-            },
-        },
         ---@diagnostic disable: missing-fields
         config = {
             clangd = {