Deprecate WiFi Shield Documentation

[retiutut]

The WiFi shield documentation and references to using the WiFi shield in other Docs pages should be deprecated.

Also, the core docs are extensive and possibly confusing.

Making this change now in Q4 2021 will improve the overall clarity and ease-of-use for the Docs.

This is a larger project that will require searching/reading references in other docs.

Things to look for:

• Pictures in other docs that mention the WiFi shield
• Moving core WiFi shield docs to deprecated
• Whole sections of other docs that differentiate instructions solely for coupling with the WiFi shield
• References to being able to use higher sampling rates for Ganglion and Cyton

[retiutut]

This issue is officially on hold, pending more information from the OpenBCI team on next steps regarding the WiFi shield.