Fixed app navigation for IE11

[skjnldsv]

Fixesnextcloud/calendar#742
Fixes https://help.nextcloud.com/t/bug-help-the-latest-updates-to-contacts-only-spins/27521/

See https://caniuse.com/#feat=flexbox

IE 11 requires a unit to be added to the third argument, the flex-basis property see MSFT documentation

@nextcloud/designers

[codecov]

Codecov Report

Merging #8573 into master will decrease coverage by 45.3%.
The diff coverage is n/a.

@@ Coverage Diff @@## master #8573 +/- ##
============================================
- Coverage 51.9% 6.6% -45.31% 
Complexity 25434 25434 ============================================
Files 1609 1609 Lines 95365 95365 Branches 1378 1378 ============================================
- Hits 49502 6300 -43202 - Misses 45863 89065 +43202

Impacted Files	Coverage Δ	Complexity Δ
lib/private/DB/QueryBuilder/Parameter.php	0% <0%> (-100%)	2% <0%> (ø)
...te/Authentication/Token/DefaultTokenCleanupJob.php	0% <0%> (-100%)	1% <0%> (ø)
apps/files_versions/lib/AppInfo/Application.php	0% <0%> (-100%)	2% <0%> (ø)
apps/dav/lib/CalDAV/PublicCalendarObject.php	0% <0%> (-100%)	1% <0%> (ø)
lib/private/Group/Database.php	0% <0%> (-100%)	26% <0%> (ø)
lib/private/Hooks/LegacyEmitter.php	0% <0%> (-100%)	1% <0%> (ø)
...pFramework/Db/MultipleObjectsReturnedException.php	0% <0%> (-100%)	1% <0%> (ø)
apps/dav/lib/CalDAV/Activity/Setting/Calendar.php	0% <0%> (-100%)	8% <0%> (ø)
apps/files/lib/Activity/Settings/FileCreated.php	0% <0%> (-100%)	8% <0%> (ø)
lib/private/Session/Session.php	0% <0%> (-100%)	5% <0%> (ø)
... and 867 more

[MorrisJobke]

Tested in IE11 and works 👍

[skjnldsv]

One more review?

[skjnldsv]

Failure also unrelated