Remove "paste on set clipboard" feature

Now that content is pasted on Ctrl+v, the hack to send the PASTE keycode
(for Android >= 7 only) is obsolete. Remove it.

This reverts fc1dec0270.

app/src/control_msg.c

@@ -67,11 +67,10 @@ control_msg_serialize(const struct control_msg *msg, unsigned char *buf) {
                              (uint32_t) msg->inject_scroll_event.vscroll);
             return 21;
         case CONTROL_MSG_TYPE_SET_CLIPBOARD: {
-            buf[1] = !!msg->set_clipboard.paste;
             size_t len = write_string(msg->set_clipboard.text,
                                       CONTROL_MSG_CLIPBOARD_TEXT_MAX_LENGTH,
-                                      &buf[2]);
-            return 2 + len;
+                                      &buf[1]);
+            return 1 + len;
         }
         case CONTROL_MSG_TYPE_SET_SCREEN_POWER_MODE:
             buf[1] = msg->set_screen_power_mode.mode;