remove roles from users when role is deleted

[kevinpapst]

Description

Fixes #1588

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• I verified that my code applies to the guidelines (composer kimai:code-check)
• I updated the documentation (see here)
• I agree that this code is used in Kimai and will be published under the MIT license

[codecov]

Codecov Report

Merging #1640 into master will increase coverage by 0.00%.
The diff coverage is 92.85%.

@@            Coverage Diff            @@
##             master    #1640   +/-   ##
=========================================
  Coverage     92.17%   92.17%           
- Complexity     4774     4777    +3     
=========================================
  Files           443      443           
  Lines         14787    14800   +13     
=========================================
+ Hits          13630    13642   +12     
- Misses         1157     1158    +1     

Impacted Files	Coverage Δ	Complexity Δ
src/Repository/UserRepository.php	83.33% <88.88%> (+0.38%)	39.00 <2.00> (+2.00)
src/Controller/PermissionController.php	93.26% <100.00%> (+0.26%)	24.00 <3.00> (+1.00)