partials/tabs/mentors.html: Change page for GSoC 2019 mentors

Replacing static text from 2018 to 2019

Closes: coala#777

Author: chttrjeankr

partials/tabs/mentors.html

@@ -4,7 +4,7 @@
     <div class="col m8 offset-m2">
       <h1 class="fine center">Hello there!</h1>
       <h4 class="light center">
-        We are the mentors for coala in GSoC 2018.
+        We are the mentors for coala in GSoC 2019.
       </h4>
       <h4 class="light center">
         Just drop a message on <a href="https://coala.io/chat" class="bear-link">Gitter</a> -
@@ -42,7 +42,7 @@ <h4 class="light center">
     <div class="col m8 offset-m2">
       <h1 class="fine center">Admins</h1>
       <h4 class="light center">
-        We are the admins for coala in GSoC 2018.
+        We are the admins for coala in GSoC 2019.
       </h4>
       <h4 class="light center">
         Just drop a message on <a href="https://coala.io/chat" class="bear-link">Gitter</a>