Revert stack version pinning for packages failing with 9.x

[jsoriano]

When updating default stack version to 9.x we had to pin the stack version for some test packages in 8.x, because they were failing with 9.x.

Most of the cases are apparently related to https://github.com/elastic/security-integrations/issues/289.

Revert the stack versions pinned in #2763 when the issues are fixed.

[mrodm]

The stack version is required to be pinned for a new package (ti_anomali_template) #2973 , and it should also be reverted as part of this issue.