[fix] Do not use string-replace

Because there is no `string-replace` in the Emacs27
Fixes https://t.me/emacs_telega/44040

telega-ins.el

@@ -135,7 +135,7 @@ Activates box button if cursor enter, deactivates if leaves."
   ;; NOTE: buttons must not be breakable by filling logic, so we use
   ;; non-breakable spaces instead of regular
   (apply #'telega-ins--text-button
-         (string-replace " " telega-symbol-nbsp label) props))
+         (replace-regexp-in-string " " telega-symbol-nbsp label) props))
 
 (defun telega-ins--image (img &optional slice-num &rest props)
   "Insert image IMG generated by telega.

test.el

@@ -244,6 +244,13 @@ Have Stoploss 690 Satoshi." :entities []))))
                                 :text)))
   )
 
+(ert-deftest telega-inserters-old-emacs ()
+  ;; NOTE: `telega-ins--text-button' has been in use of
+  ;; `string-replace' that is not in emacs27
+  ;; ref: https://t.me/emacs_telega/44040
+  (should (equal (progn (telega-ins--box-button "test here") 'aa)
+                 'aa)))
+
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