Clean up config help text

[wagoodman]

Today we use the options structs from each command registered with clio to build the output of the grype config command. However, not all commands are meant to support options being configured via a config file -- but these are being shown in the grype config output anyway:

# og-config is `grype config` with the latest grype release
# new-config is `grype config` with grype built from this branch
diff /tmp/og-config /tmp/new-config

228,236d227
< 
< # delete downloaded databases after diff occurs (env: GRYPE_DELETE)
< delete: false
< 
< # format to display results (available=[table, json]) (env: GRYPE_OUTPUT)
< Output: 'table'
< 
< # CVE IDs to explain (env: GRYPE_CVE_IDS)
< cve-ids: []

Note that Output is for grype db * commands and there is still an output value documented in the grype config output.

This PR removes all subcommands from consideration when generating grype config output.

[wagoodman]

looks like there is something I didn't take into consideration -- I'll take a closer look later today