fix(endpoints): correct epersons, groups, securitysettings

[MMilosz]

All three verified with sandbox.dspace.org/server. Corrections were not needed in epersons.md, securitysettings-endpoint.md & epersongroups.md

Before	After
/api/core/epersons (404)	/api/eperson/epersons (200)
/api/core/groups (404)	/api/eperson/groups (200)
/api/core/groups/securitysettings/Publication (404)	/api/core/securitysettings/Publication (200)

[tdonohue]

👍 Thanks @MMilosz ! This is obviously a correct fix.

[dspace-bot]

Backport failed for dspace-8_x, because it was unable to cherry-pick the commit(s).

Please cherry-pick the changes locally and resolve any conflicts.

git fetch origin dspace-8_x
git worktree add -d .worktree/backport-390-to-dspace-8_x origin/dspace-8_x
cd .worktree/backport-390-to-dspace-8_x
git switch --create backport-390-to-dspace-8_x
git cherry-pick -x 248a4fb7d57226d1b676251bb5096a4f3e67cb05

[dspace-bot]

Backport failed for dspace-9_x, because it was unable to cherry-pick the commit(s).

Please cherry-pick the changes locally and resolve any conflicts.

git fetch origin dspace-9_x
git worktree add -d .worktree/backport-390-to-dspace-9_x origin/dspace-9_x
cd .worktree/backport-390-to-dspace-9_x
git switch --create backport-390-to-dspace-9_x
git cherry-pick -x 248a4fb7d57226d1b676251bb5096a4f3e67cb05

[dspace-bot]

Successfully created backport PR for dspace-10_x:

• [Port dspace-10_x] fix(endpoints): correct epersons, groups, securitysettings #391