Fix popover and styling in user management

[juliusknorr]

• Fix popover positioning
• Always show the 3-dots icon
• Remove margin between new user form and table

Before:

After:

@nextcloud/designers

[skjnldsv]

Popover fix already included in the new user menu pr I did! :)

[MorrisJobke]

Popover fix already included in the new user menu pr I did! :)

But it will not go into Nextcloud 13 ;)

[skjnldsv]

But it will not go into Nextcloud 13 ;)

It could! :'(
But I like this fix better! LGTM!

[codecov]

Codecov Report

Merging #7790 into master will decrease coverage by 2.02%.
The diff coverage is 0%.

@@ Coverage Diff @@## master #7790 +/- ##
============================================
- Coverage 53.24% 51.22% -2.03% - Complexity 23656 24968 +1312 
============================================
Files 1514 1607 +93 Lines 88252 95007 +6755 Branches 1376 1376 ============================================
+ Hits 46994 48669 +1675 - Misses 41258 46338 +5080

Impacted Files	Coverage Δ	Complexity Δ
settings/templates/users/part.userlist.php	0% <0%> (ø)	0 <0> (ø)	⬇️
.../tests/Unit/Collaboration/CommentersSorterTest.php	25.55% <0%> (-66.45%)	6% <0%> (ø)
apps/sharebymail/tests/SettingsTest.php	52.17% <0%> (-47.83%)	3% <0%> (ø)
lib/private/Security/RateLimiting/Limiter.php	55.55% <0%> (-44.45%)	5% <0%> (ø)
settings/Controller/EncryptionController.php	54.71% <0%> (-38.84%)	8% <0%> (ø)
settings/Controller/GroupsController.php	64.61% <0%> (-35.39%)	9% <0%> (ø)
...ps/comments/tests/Unit/AppInfo/ApplicationTest.php	69.56% <0%> (-30.44%)	4% <0%> (ø)
lib/private/AvatarManager.php	71.42% <0%> (-28.58%)	4% <0%> (ø)
apps/user_ldap/lib/Configuration.php	42.02% <0%> (-27.86%)	87% <0%> (ø)
apps/encryption/lib/Command/EnableMasterKey.php	75% <0%> (-25%)	5% <0%> (ø)
... and 282 more

[MorrisJobke]

Tested and works 👍