The ambiguous operator warnings should only be shown if $VERBOSE is true

Author: eregon

src/main/java/org/truffleruby/parser/lexer/RubyLexer.java

@@ -122,11 +122,11 @@ private ComplexParseNode newComplexNode(NumericParseNode number) {
     }
 
     protected void ambiguousOperator(String op, String syn) {
-        warnings.warn(
+        warnings.warning(
                 getFile(),
                 getPosition().toSourceSection(src.getSource()).getStartLine(),
                 "`" + op + "' after local variable or literal is interpreted as binary operator");
-        warnings.warn(
+        warnings.warning(
                 getFile(),
                 getPosition().toSourceSection(src.getSource()).getStartLine(),
                 "even though it seems like " + syn);