doc: update file keywords v3

[jmtaylor90]

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• I have read the contributing guide lines at https://docs.suricata.io/en/latest/devguide/codebase/contributing/contribution-process.html
• I have signed the Open Information Security Foundation contribution agreement at https://suricata.io/about/contribution-agreement/
• I have updated the user guide (in doc/userguide/) to reflect the changes made (if applicable)

Link to redmine ticket:

Describe changes:

• Update file.magic and file.name keyword information to reflect recent updates
• Update libmagic dependency information and reference
• Address review comments in doc: update file keywords v2 #9316

Provide values to any of the below to override the defaults.

To use a pull request use a branch name like pr/N where N is the
pull request number.

Alternatively, SV_BRANCH may also be a link to an
OISF/suricata-verify pull-request.

SV_REPO=
SV_BRANCH=
SU_REPO=
SU_BRANCH=
LIBHTP_REPO=
LIBHTP_BRANCH=

[jufajardini]

Looks good to me, thanks for your time incorporating all the feedback! :)

[jmtaylor90]

Seeing as the code is being backported to the 6.x series, do we want a backport of these docs as well?

[jufajardini]

Seeing as the code is being backported to the 6.x series, do we want a backport of these docs as well?

Yes, that'd be good, thanks :)

[victorjulien]

Merged in #9355, thanks!