Update deprecated TSF scope

The Windows Text Services Framework (TSF) handles text completion
suggestions. It has different modes depending on what kind of data is
being typed (numeric, email, private/non-private etc), which is handled
by passing a "scope" enum.

`tsf_input_scope.cc` is currently incorrectly passing `IS_PASSWORD` as
the scope for password fields, which is deprecated and not handled correctly (see bug). This CL changes `IS_PASSWORD` to `IS_PRIVATE`.

Bug: 430987831

Change-Id: I8441287615b6cb4a5cc06cd08ecfa521ae311dc7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6783020
Reviewed-by: Karol Sygiet <sygiet@google.com>
Reviewed-by: Colin Blundell <blundell@chromium.org>
Commit-Queue: Teo Lamort de Gail <lamort@google.com>
Cr-Commit-Position: refs/heads/main@{#1491395}