[analyzer] Nit: Doc: Add missing FunctionBody.
[analyzer] Nit: Doc: Add missing FunctionBody.

Change-Id: Ia63b9828452161b891e58052137870bb2866d672
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/220010
Auto-Submit: Clement Skau <495593248b6158163719b90dde8357b589c8e5d0@google.com>
Commit-Queue: Konstantin Shcheglov <09e4d7516628963212bf4aace2f97603d2b706e4@google.com>
Reviewed-by: Konstantin Shcheglov <09e4d7516628963212bf4aace2f97603d2b706e4@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk