Remove db optimization as cimq/postgres do not support ramdisk

[nanophate]

Description

Deleting ramdisk optimization options

Reasons

circleci/postgres had an option to support ramdisk PGDATA: /dev/shm/pgdata/data but when we switched to a new convenience image cimg/postgres it was discussed on CircleCI-Public/cimg-postgres#2 that ramdisk will not be supported.

Content Checklist

Please follow our style when contributing to CircleCI docs. Our style guide is here: https://circleci.com/docs/style/style-guide-overview.

Please take a moment to check through the following items when submitting your PR (this is just a guide so will not be relevant for all PRs) 😸:

• Break up walls of text by adding paragraph breaks.
• Consider if the content could benefit from more structure, such as lists or tables, to make it easier to consume.
• Keep the title between 20 and 70 characters.
• Consider whether the content would benefit from more subsections (h2-h6 headings) to make it easier to consume.
• Check all headings h1-h6 are in sentence case (only first letter is capitalized).
• Is there a "Next steps" section at the end of the page giving the reader a clear path to what to read next?
• Include relevant backlinks to other CircleCI docs/pages.

[FelicianoTech]

I'm for removing this. None of the next-gen Convenience Images (cimg) use ramdisk. So if we mention this for MariaDB/MySQL/Reddis as well, those can also be removed.

[devinmarieb]

@nanophate this PR is failing the build process because of this issue here (something is not logged in properly for your user)
https://support.circleci.com/hc/en-us/articles/360043002793-Troubleshooting-CircleCI-Access-After-Enabling-Github-SSO