Fix license url according to spdx license spec

[StefMa]

Somewhat of a follow-up of #3134 😅 Sorry ✌️

The reasining behind this PR is the same as #3134.
But this time it fixes the URL to the license.
Since mockito uses the standard MIT license without any modifications it should point to the "original"/"trusted"/"well known" license url, so that other plugins or tools can rely on this and make sure that mockito is using the original MIT license without any modifications 👍

Checklist

• Read the contributing guide
• PR should be motivated, i.e. what does it fix, why, and if relevant how
• If possible / relevant include an example in the description, that could help all readers
  including project members to get a better picture of the change
• Avoid other runtime dependencies
• Meaningful commit history ; intention is important please rebase your commit history so that each
  commit is meaningful and help the people that will explore a change in 2 years
• The pull request follows coding style
• Mention Fixes #<issue number> in the description if relevant
• At least one commit should mention Fixes #<issue number> if relevant

[codecov-commenter]

Codecov Report

All modified lines are covered by tests ✅

Comparison is base (73d6afc) 85.53% compared to head (2802037) 85.06%.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #3152      +/-   ##
============================================
- Coverage     85.53%   85.06%   -0.48%     
+ Complexity     2912     2898      -14     
============================================
  Files           333      333              
  Lines          8856     8856              
  Branches       1095     1095              
============================================
- Hits           7575     7533      -42     
- Misses          993     1046      +53     
+ Partials        288      277      -11     

see 8 files with indirect coverage changes

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