perlre: Update obsolete example

/foo{4,3}/ now emits a message, contrary to what the pod claims.  Use a
different example that doesn't emit a message

Author: khwilliamson

pod/perlre.pod

@@ -543,11 +543,10 @@ character.  In particular, the lower quantifier bound is not optional,
 and a typo in a quantifier silently causes it to be treated as the
 literal characters.  For example,
 
-    /o{4,3}/
+    /o{4,a}/
 
-looks like a quantifier that matches 0 times, since 4 is greater than 3,
-but it really means to match the sequence of six characters
-S<C<"o { 4 , 3 }">>.  It is planned to eventually require literal uses
+compiles to match the sequence of six characters
+S<C<"o { 4 , a }">>.  It is planned to eventually require literal uses
 of curly brackets to be escaped, say by preceding them with a backslash
 or enclosing them within square brackets, (C<"\{"> or C<"[{]">).  This
 change will allow for future syntax extensions (like making the lower