doc: Fixing Javadoc formatting problems.

No code changes, just fixing typos in the doc comments.

Doc is staged to:

http://go/dac-stage/reference/android/service/autofill/AutofillService.html
http://go/dac-stage/reference/android/service/autofill/FillRequest.html

Test: make ds-docs
Bug: 70812346
Merged-In: Ia76121c60197275c6be1717c8003fe1c4baf5f97
Change-Id: I5ee04bb96234441c5740665540b5e803fcf9710f