doc: update FAQ to mention aqa-tests branches

[sxa]

Based on things seen in:

• Update Temurin linux builds to use suggested Security Audit gcc compiler flags temurin-build#3685 (comment)
• Set up Ubuntu 24.04 systems to be able to support it for Temurin #3501 (comment)
• Triage for Amazon Linux 2023 ( Docker static) aqa-tests#5300 (comment)

Checklist

• commit message has one of the standard prefixes
• faq.md updated if appropriate
• other documentation is changed or added (if applicable)
• playbook changes run through VPC or QPC (if you have access)
• VPC/QPC not applicable for this PR
• for inventory.yml changes, bastillion/nagios/jenkins updated accordingly

[karianna]

Style suggestion (active voice) - could change to:

then the process is typically like this. To avoid the test material not
matching the JDK under test which can lead to false failures when you're
testing a build which isn't the latest (such as a previous GA/the last release),
it is recommended that you check out the appropriate branch for the last release
from the aqa-tests repository in the first line here.

[sxa]

Style suggestion (active voice) - could change to:

I have no preference, so I've switched the wording to what you've recommended.