Prefer incf to cl-incf in textmodes/*.el

Prefer incf to cl-incf in textmodes/*.el

* lisp/textmodes/css-mode.el (css--rgb-color):
* lisp/textmodes/reftex-dcr.el (reftex-view-regexp-match):
* lisp/textmodes/reftex-global.el (reftex-find-duplicate-labels)
(reftex-renumber-simple-labels, reftex-translate):
* lisp/textmodes/reftex-index.el (reftex-index-select-tag)
(reftex-index-phrases-info, reftex-query-index-phrase):
* lisp/textmodes/reftex-parse.el (reftex-where-am-I)
(reftex-what-macro, reftex-nth-arg, reftex-section-number):
* lisp/textmodes/reftex-ref.el (reftex-uniquify-label):
* lisp/textmodes/reftex-sel.el (reftex-insert-docstruct):
* lisp/textmodes/reftex.el (reftex-next-multifile-index)
(reftex-compile-variables, reftex-parse-args)
(reftex-select-external-document):
* lisp/textmodes/rst.el (rst-display-hdr-hierarchy)
(rst-toc-insert-children, rst-apply-indented-blocks)
(rst-enumerate-region, rst-convert-bullets-to-enumeration):
* lisp/textmodes/tex-mode.el (tex-count-words): Prefer incf to cl-incf.

(cherry picked from commit 0eada9e1d30b9072cdc1bf8388205773cd23986f)