chore: fix sponsor link

BACKERS.md

@@ -235,7 +235,7 @@ Funds donated via Patreon go directly to support Evan You's full-time work on Vu
         </a>
       </td>
       <td align="center" valign="middle">
-        <a href="https:/www.programmers.io" target="_blank">
+        <a href="https://www.programmers.io" target="_blank">
           <img width="148px" src="https://raw.githubusercontent.com/vuejs/vuejs.org/master/themes/vue/source/images/programmers_io.png">
         </a>
       </td>

README.md

@@ -240,7 +240,7 @@ Funds donated via Patreon go directly to support Evan You's full-time work on Vu
         </a>
       </td>
       <td align="center" valign="middle">
-        <a href="https:/www.programmers.io" target="_blank">
+        <a href="https://www.programmers.io" target="_blank">
           <img width="148px" src="https://raw.githubusercontent.com/vuejs/vuejs.org/master/themes/vue/source/images/programmers_io.png">
         </a>
       </td>