fix: Use = and length separately instead of length=

length= does not exist on 27.2 and older Emacs versions.

It was added in Emacs 28.1 in
https://git.savannah.gnu.org/cgit/emacs.git/commit/?id=9809f7ed2c639bd51abd4a28bd5d1a37f0d46a3d.

tomelr.el

@@ -277,16 +277,17 @@ non-nil.  Sorting can optionally be DESTRUCTIVE for speed."
 (defun tomelr--print-array (array)
   "Like `tomelr-encode-array', but insert the TOML at point."
   (insert "[ ")
-  (unless (length= array 0)
+  (unless (= 0 (length array))
     (tomelr--with-indentation
       (let ((first t))
         (mapc (lambda (elt)
                 (if first
                     (setq first nil)
                   (insert ", "))
                 (tomelr--print elt))
-              array))))
-  (insert " ]"))
+              array)))
+    (insert " "))
+  (insert "]"))
 
 (defun tomelr-encode-array (array)
   "Return a TOML representation of ARRAY.