DOC-1993 switched to lowercase for geo units

[andy-stark-redis]

DOC-1993 Some of these commands say in the history that they now support uppercase units but it seemed reasonable to change the syntax docs to keep things consistent.

Also, I assume that the M, KM, etc, in the token metadata doesn't need to change just to update the Syntax section?

[github-actions[bot]]

Staging links:
https://redis.io/docs/staging/DOC-1993-geo-dist-units/commands/geodist/
https://redis.io/docs/staging/DOC-1993-geo-dist-units/commands/georadius/
https://redis.io/docs/staging/DOC-1993-geo-dist-units/commands/georadius_ro/
https://redis.io/docs/staging/DOC-1993-geo-dist-units/commands/georadiusbymember/
https://redis.io/docs/staging/DOC-1993-geo-dist-units/commands/georadiusbymember_ro/
https://redis.io/docs/staging/DOC-1993-geo-dist-units/commands/geosearch/
https://redis.io/docs/staging/DOC-1993-geo-dist-units/commands/geosearchstore/

[andy-stark-redis]

Thanks @dwdougherty !