Disable automatic call to flyspell-buffer

Some users complained about slowness when opening files due to
spell-checking being activated. This commit revert to old behaviour
checking only the words under the cursor and not the whole buffer.

layers/spell-checking/README.org

@@ -84,6 +84,7 @@ currently supported language:
 
 | Key Binding | Description              |
 |-------------+--------------------------|
+| ~SPC S b~   | flyspell whole buffer    |
 | ~SPC S c~   | flyspell correct         |
 | ~SPC S d~   | change dictionary        |
 | ~SPC S n~   | flyspell goto next error |

layers/spell-checking/packages.el

@@ -61,6 +61,7 @@
         :evil-leader "tS")
 
       (evil-leader/set-key
+        "Sb" 'flyspell-buffer
         "Sd" 'spell-checking/change-dictionary
         "Sn" 'flyspell-goto-next-error))
     :config