RenderTarget data for default reflection probe is not updated when some modifications are done over skybox material shaders unless the resolution is changed or Unity editor is rebooted.

Steps for reproduction:
1) Open the scene “Example”
2) Disable Auto mode and Generate Lighting
3) Check the Reflection Probe under Example folder
4) Open StarNestSkybox shader
5) Comment out line 190 (return float4(v * .01, 1.0);)
6) Remove the comments for line 191 (return 0.5.xxxx;)
7) Generate Lighting again
8) Observe that the data for Reflection Probes is not updated (old data remains intact)

Notes:
- Changing the Resolution parameter under Environment Reflections section in Lighting window updates the reflection probe correctly. However, issue persists as long as the resolution parameter is not changed
- As another workaround, rebooting Unity editor fixes the issue
- Not a regression, issue is related to how GI data is cached in runtime memory