[gitpod] trigger rebuild to pick upstream image changes

particularly:
- vnc reconnect fix
- python config for npm fix

Signed-off-by: Anton Kosyakov <anton.kosyakov@typefox.io>

.gitpod.dockerfile

@@ -1,7 +1,7 @@
 FROM gitpod/workspace-full-vnc:latest
 
 # Docker build does not rebuild an image when a base image is changed, increase this counter to trigger it.
-ENV TRIGGER_REBUILD 2
+ENV TRIGGER_REBUILD 3
 
 # Install custom tools, runtime, etc.
 RUN sudo apt-get update \