Cover go.mod and go.sum in .editorconfig (#33960)

These files were previously set to use spaces for indendation but they
are supposed to use tabs, so set this in editorconfig.

Author: silverwind

.editorconfig

@@ -12,6 +12,9 @@ insert_final_newline = true
 [*.{go,tmpl,html}]
 indent_style = tab
 
+[go.*]
+indent_style = tab
+
 [templates/custom/*.tmpl]
 insert_final_newline = false