Fix app nav img margin

[skjnldsv]

Fix#6622
@nextcloud/designers

[juliusknorr]

@skjnldsv Also happens to be an issue without an image, see the app management:

[skjnldsv]

@juliushaertl This is @jancborchardt's will. He wants users to be 'forced' to have some icons! :)
#6399 (comment)

[juliusknorr]

Ah ok, is there already an issue for the parts missing an icon in the server repo?

[skjnldsv]

You mean in the apps management section?

[codecov]

Codecov Report

Merging #6623 into master will decrease coverage by <.01%.
The diff coverage is n/a.

@@ Coverage Diff @@## master #6623 +/- ##
============================================
- Coverage 53.06% 53.06% -0.01% 
Complexity 22553 22553 ============================================
Files 1414 1414 Lines 87745 87745 Branches 1340 1340 ============================================
- Hits 46565 46564 -1 - Misses 41180 41181 +1

Impacted Files	Coverage Δ	Complexity Δ
apps/files_trashbin/lib/Trashbin.php	72.28% <0%> (-0.25%)	136% <0%> (ø)

[skjnldsv]

@nextcloud/designers please review :)

[juliusknorr]

@skjnldsv Yes. Found it #3987

[jancborchardt]

@skjnldsv see, it pushes us to add icons ;)

[skjnldsv]

@jancborchardt well done fine sir! You tricked me well! 😱😱