Fix incorrect Javadoc inline tag for MockitoJUnitRunner

[Marcono1234]

Fixes incorrect usage of the {@code ...} Javadoc inline tag. As part of that the @ had to be replaced with @ because {@code ...} treats its content literally.

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

Base: 86.18% // Head: 86.18% // No change to project coverage 👍

Coverage data is based on head (4ba5cfe) compared to base (2567f05).
Patch has no changes to coverable lines.

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #2816   +/-   ##
=========================================
  Coverage     86.18%   86.18%           
  Complexity     2833     2833           
=========================================
  Files           320      320           
  Lines          8586     8586           
  Branches       1060     1060           
=========================================
  Hits           7400     7400           
  Misses          905      905           
  Partials        281      281           

Impacted Files	Coverage Δ
...ain/java/org/mockito/junit/MockitoJUnitRunner.java	100.00% <ø> (ø)

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[TimvdLippe]

Thanks!