Add CAP_SYS_TIME to FTL's ambient capabilities

[DL6ER]

What does this implement/fix?

This PR accompanies and grants FTL time setting capabilities needed for continuous background time synchronizations added in pi-hole/FTL#1977

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Related issue or feature (if applicable): N/A

Pull request in docs with documentation (if applicable): N/A

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1. I have read and understood the contributors guide, as well as this entire template. I understand which branch to base my commits and Pull Requests against.
2. I have commented my proposed changes within the code.
3. I am willing to help maintain this change if there are issues with it later.
4. It is compatible with the EUPL 1.2 license
5. I have squashed any insignificant commits. (git rebase)

Checklist:

• The code change is tested and works locally.
• I based my code and PRs against the repositories developmental branch.
• I signed off all commits. Pi-hole enforces the DCO for all contributions
• I signed all my commits. Pi-hole requires signatures to verify authorship
• I have read the above and my PR is ready for review.

[yubiuser]

Also needs to be ported to https://github.com/pi-hole/docker-pi-hole/blob/60d8067d755419708bb49b215650bd33aa7f0270/src/bash_functions.sh#L105

[DL6ER]

Test falling because of

#6 [2/6] RUN yum install -y git initscripts
#6 0.656 CentOS Stream 8 - AppStream                     121  B/s |  38  B     00:00    
#6 0.662 Error: Failed to download metadata for repo 'appstream': Cannot prepare internal mirrorlist: No URLs in mirrorlist
#6 ERROR: process "/bin/sh -c yum install -y git initscripts" did not complete successfully: exit code: 1

[rdwebdesign]

CentOS Stream 8 is EOL:

• https://www.centos.org/cl-vs-cs/#end-of-life
• https://endoflife.date/centos-stream