Fix Javadoc invalid syntax

[chmielowiec]

Escape @ character to html entity.

Fixes #1977

[TimvdLippe]

Good catch, thanks!

[codecov-commenter]

Codecov Report

Merging #1978 into release/3.x will increase coverage by 0.02%.
The diff coverage is n/a.

@@                Coverage Diff                @@
##             release/3.x    #1978      +/-   ##
=================================================
+ Coverage          85.41%   85.44%   +0.02%     
  Complexity          2601     2601              
=================================================
  Files                322      322              
  Lines               7496     7496              
  Branches             897      897              
=================================================
+ Hits                6403     6405       +2     
  Misses               855      855              
+ Partials             238      236       -2     

Impacted Files	Coverage Δ	Complexity Δ
src/main/java/org/mockito/Mockito.java	95.23% <ø> (ø)	45.00 <0.00> (ø)
...to/internal/util/concurrent/WeakConcurrentMap.java	41.48% <0.00%> (+2.12%)	11.00% <0.00%> (ø%)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 6635dee...967a94c. Read the comment docs.