[CBRD-24941] slip: revert the use of '%' as the modular operator (#5706)

revert the use of '%' as the modular operator because it confuses the lexer with the presence of cursor attributes and %type and %rowtype.

pl_engine/pl_server/src/main/antlr/PlcLexer.g4

@@ -100,7 +100,7 @@ LANGUAGE:                     L A N G U A G E ;
 LIKE:                         L I K E ;
 LIST:                         L I S T ;
 LOOP:                         L O O P ;
-MOD:                          ( M O D | '%' ) ;
+MOD:                          M O D ;
 MULTISET:                     M U L T I S E T ;
 NOT:                          N O T ;
 NULL_:                        N U L L ;