Remove .projects-search-form

Signed-off-by: Takuya Noguchi <takninnovationresearch@gmail.com>

app/assets/stylesheets/framework/mobile.scss

@@ -56,10 +56,4 @@
   .activity-filter-block {
     display: none;
   }
-
-  .projects-search-form {
-    .btn {
-      display: none;
-    }
-  }
 }