Add DoNotMock mention to main JavaDoc

[TimvdLippe]

I forgot to add the DoNotMock feature to the main JavaDoc in #1833

[codecov-commenter]

Codecov Report

Merging #2512 (167859a) into main (b91bd29) will decrease coverage by 0.20%.
The diff coverage is n/a.

❗ Current head 167859a differs from pull request most recent head 7e62cec. Consider uploading reports for the commit 7e62cec to get more accurate results

@@             Coverage Diff              @@
##               main    #2512      +/-   ##
============================================
- Coverage     86.66%   86.45%   -0.21%     
+ Complexity     2781     2779       -2     
============================================
  Files           320      320              
  Lines          8344     8344              
  Branches       1022     1022              
============================================
- Hits           7231     7214      -17     
- Misses          842      859      +17     
  Partials        271      271              

Impacted Files	Coverage Δ
src/main/java/org/mockito/Mockito.java	92.20% <ø> (ø)
...ito/internal/creation/proxy/MethodHandleProxy.java	54.54% <0.00%> (-45.46%)	⬇️
...ckito/internal/creation/proxy/ProxyRealMethod.java	42.85% <0.00%> (-28.58%)	⬇️

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