Update javadocs for GHPullRequestFileDetail

[t0m4uk1991]

Description

In order to fix #486, JavaDocs for GHPullRequestFileDetail was updated.

Fixes #486.

[codecov]

Codecov Report

Merging #1189 (01e25d0) into main (ebdbf8f) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##               main    #1189   +/-   ##
=========================================
  Coverage     73.85%   73.85%           
  Complexity     1862     1862           
=========================================
  Files           188      188           
  Lines          6181     6181           
  Branches        368      368           
=========================================
  Hits           4565     4565           
  Misses         1395     1395           
  Partials        221      221           

Impacted Files	Coverage Δ
...rc/main/java/org/kohsuke/github/GHPullRequest.java	76.97% <ø> (ø)
...va/org/kohsuke/github/GHPullRequestFileDetail.java	0.00% <ø> (ø)

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