Change warning for pragmas inside functions

Follow-up to 35e2b11d.

Put the warning "pragmas are ignored inside functions" inside the Unnamed
category, so that it is displayed by default and cannot be disabled.

cparser/Elab.ml

@@ -2872,7 +2872,7 @@ let elab_definition (for_loop: bool) (local: bool) (nonstatic_inline: bool)
   (* pragma *)
   | PRAGMA(s, loc) ->
       if local then
-        warning loc Unknown_pragmas "pragmas are ignored inside functions"
+        warning loc Unnamed "pragmas are ignored inside functions"
       else
         emit_elab env loc (Gpragma s);
       ([], env)