Fixed a typo in form-contact.html (#266)

layouts/shortcodes/form-contact.html

@@ -15,6 +15,6 @@
     <label class="{{ $.Scratch.Get "labelClasses" }}" for="message">{{ i18n "message" }}</label>
     <textarea id="message" name="message" class="{{ $.Scratch.Get "inputClasses" }} h4" aria-labelledby="message"></textarea>
 
-    <input class="db w-100 mv2 white pa3 bn hover-shadow hover-bg-blck bg-animate bg-black" type="submit" value="{{ i18n "send" }}" />
+    <input class="db w-100 mv2 white pa3 bn hover-shadow hover-bg-black bg-animate bg-black" type="submit" value="{{ i18n "send" }}" />
 
 </form>