VACMS-18705: Upgrade memcache and memcache_admin modules.

[anantais]

Description

Closes #18705

Testing done

Verified that memcache and memcache_admin have upgraded to version 2.6.0 without error.

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[anantais]

Removed patch because it did not allow me to upgrade to 2.6.0 and the latest comment on the patch seems to indicate that this is no longer a critical issue: https://www.drupal.org/project/memcache/issues/3058121

"Also, since the memcache extension has been working quite nicely with PHP 8 since 2020 and version 8 of the extension, and features are almost never critical anyway, downgrading from critical to normal"