Remove AutofillDataModel::IsDeletable()

Let's avoid virtual functions in AutofillDataModel:
- For the address case, no override exists and the one line
  implementation is inlined in the deduplication logic (the only use).
- For cards, the one line implementation is inlined in its override.
- For IBANs, no usages exist.

Bug: 40100455
Change-Id: I950cb0bb85f2e1ee7b7ff4c1f33a4c16982617df
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5736138
Commit-Queue: Florian Leimgruber <fleimgruber@google.com>
Reviewed-by: Jan Keitel <jkeitel@google.com>
Commit-Queue: Jan Keitel <jkeitel@google.com>
Auto-Submit: Florian Leimgruber <fleimgruber@google.com>
Code-Coverage: findit-for-me@appspot.gserviceaccount.com <findit-for-me@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/heads/main@{#1332237}