Fix @return docs on HttpCache::restoreResponseBody()
minor #11981 Fix @return docs on HttpCache::restoreResponseBody() (znerol)

This PR was submitted for the master branch but it was merged into the 2.3 branch instead (closes #11981).

Discussion
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Fix @return docs on HttpCache::restoreResponseBody()

Commits
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37dc57b Fix @return docs on HttpCache::restoreResponseBody()