Remove EOL software from drone

[solracsf]

Summary

Removes:

• MariaDB 10.2 - https://mariadb.org/about/#maintenance-policy
• Postgres 10 - https://www.postgresql.org/support/versioning/

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)

[nickvergessen]

• MariaDB 10.2 seems okay, it's also not listed anymore in https://docs.nextcloud.com/server/26/admin_manual/installation/system_requirements.html But I guess we need to have an admin check that shows a warning in that case.
• Postgres 10 is still listed as supported there as well, so also would need an admin check and docs adjustment.

However let's see what PM says to it.

[nickvergessen]

As per above:

• Docs need updating
• Admin check needs to be adjusted (if it exists) or added
• Deprecation needs to be documented in #37039
• Deprecation needs to be communicated in the forums and docs.

[J0WI]

MariaDB 10.2 can be replaced with 10.11: nextcloud/docker-ci#532

[solracsf]

@J0WI this is adressed on a different PR here: #38161