droidstubs: clarify how to address API lints

CL authors often read over the first part and just copy-paste the command to suppress the error.

- Clarify that addressing the lint if possible is required.
- Failing that, clarify that @SuppressLint is preferred, whereas updating the baseline is for large scale suppression only (e.g. when introducing a new lint that has many pre-existing violations)

Change-Id: I7cbe3a059a9052024e6c601b9e4781ffc5333e75