Remove the now unneeded c-font-lock-flush from CC Mode.

* lisp/progmodes/cc-defs.el (c-font-lock-flush): Delete this macro.

* lisp/progmodes/cc-engine.el (c-propertize-raw-string-opener): Delete the
call to the macro.

lisp/progmodes/cc-defs.el

@@ -219,13 +219,6 @@ This variant works around bugs in `eval-when-compile' in various
 	`(cl-delete-duplicates ,cl-seq ,@cl-keys)
       `(delete-duplicates ,cl-seq ,@cl-keys))))
 
-(defmacro c-font-lock-flush (beg end)
-  "Declare the region BEG...END's fontification as out-of-date.
-On XEmacs and older Emacsen, this refontifies that region immediately."
-  (if (fboundp 'font-lock-flush)
-      `(font-lock-flush ,beg ,end)
-    `(font-lock-fontify-region ,beg ,end)))
-
 (defmacro c-point (position &optional point)
   "Return the value of certain commonly referenced POSITIONs relative to POINT.
 The current point is used if POINT isn't specified.  POSITION can be

lisp/progmodes/cc-engine.el

@@ -7259,9 +7259,7 @@ comment at the start of cc-engine.el for more info."
 	    ;; (c-put-char-property open-paren 'syntax-table '(1))
 	    )
 	  (goto-char bound))
-	nil)
-  ;; Ensure the opening delimiter will get refontified.
-    (c-font-lock-flush (1- open-quote) (1+ open-paren))))
+	nil)))
 
 (defun c-after-change-unmark-raw-strings (beg end _old-len)
   ;; This function removes `syntax-table' text properties from any raw strings