Fix emacs native compilation warning for bind-key

To reproduce, have emacs built with native compilation and notice the
compilation logs. You can then open the offending file and run `M-x
emacs-lisp-native-compile-and-load` before and after the changes to see
the warning is removed.

```
 ■  Warning (comp): bind-key.el:150:2: Warning: docstring has wrong
usage of unescaped single quotes (use \= or different quoting)
```

Author: sdwolfz

bind-key.el

@@ -158,9 +158,9 @@ COMMAND must be an interactive function or lambda form.
 KEYMAP, if present, should be a keymap variable or symbol.
 For example:
 
-  (bind-key \"M-h\" #'some-interactive-function my-mode-map)
+  (bind-key \"M-h\" #\\='some-interactive-function my-mode-map)
 
-  (bind-key \"M-h\" #'some-interactive-function \\='my-mode-map)
+  (bind-key \"M-h\" #\\='some-interactive-function \\='my-mode-map)
 
 If PREDICATE is non-nil, it is a form evaluated to determine when
 a key should be bound. It must return non-nil in such cases.