Update mission statement in footer (#2189)

src/site/includes/footer.html

@@ -6,8 +6,7 @@
 </footer>
 <div id="logout-modal-root"></div>
 <!--
-“To care for him who shall have borne the battle and for his widow, and his orphan.”
-- Abraham Lincoln
+VA's mission: To fulfill President Lincoln's promise to care for those who have served in our nation's military and for their families, caregivers, and survivors.
 -->
 <script nonce="**CSP_NONCE**" type="text/javascript">
 (function() {