[stable13] Show EOL warning in the update section

[nickvergessen]

Backport #8821

[MorrisJobke]

Tested and works 👍

[MorrisJobke]

Rebased to retrigger CI

[codecov]

Codecov Report

Merging #8986 into stable13 will decrease coverage by 16.68%.
The diff coverage is 0%.

@@               Coverage Diff               @@
##             stable13    #8986       +/-   ##
===============================================
- Coverage       51.33%   34.64%   -16.69%     
- Complexity      25040    25042        +2     
===============================================
  Files            1609     1609               
  Lines           95317    95325        +8     
  Branches         1376     1376               
===============================================
- Hits            48929    33030    -15899     
- Misses          46388    62295    +15907

Impacted Files	Coverage Δ	Complexity Δ
...atenotification/lib/Controller/AdminController.php	0% <0%> (-66.67%)	12 <0> (+1)
apps/updatenotification/templates/admin.php	0% <0%> (ø)	0 <0> (ø)	⬇️
lib/private/Updater/VersionCheck.php	0% <0%> (-92.11%)	8 <0> (+1)
apps/updatenotification/lib/UpdateChecker.php	0% <0%> (-75%)	9 <0> (ø)
...te/Authentication/LoginCredentials/Credentials.php	0% <0%> (-100%)	4% <0%> (ø)
...s/dav/lib/CalDAV/BirthdayCalendar/EnablePlugin.php	0% <0%> (-100%)	7% <0%> (ø)
...ty/Exceptions/CrossSiteRequestForgeryException.php	0% <0%> (-100%)	1% <0%> (ø)
...curity/Exceptions/StrictCookieMissingException.php	0% <0%> (-100%)	1% <0%> (ø)
apps/dav/lib/CalDAV/Activity/Setting/Calendar.php	0% <0%> (-100%)	8% <0%> (ø)
lib/private/App/AppStore/Version/Version.php	0% <0%> (-100%)	3% <0%> (ø)
... and 526 more

[nickvergessen]

Rebased and fixed the last failing test