Fix autofill copy keys and squash warnings (#3358)

Task/Issue URL:
https://app.asana.com/0/1201037661562251/1208424278203049/f

**Description**:

There were several localization warnings introduced during [✓ macOS -
Mitigate users concerns about Password Manager
security](https://app.asana.com/0/1199230911884351/1207411921782782/f)

- UserText.pmSaveCredentialsSecurityInfo and
UserText.pmSaveCredentialsSecurityInfoAutolockOff have same keys which
can‘t be localized and causes warning
- UserText.pmEmptyStateDefaultDescription has same key with
pmEmptyStateDefaultDescriptionAutolockOff

Also there were some warnings about stale strings that are no longer in
use so I removed them in the second commit.

**Steps to test this PR**:
Change to any language other than English and check:
1. The password manager empty state string (with autolock on and off).
Check links work and end up in the right place.
2. The tooltip text on the save password dialog (with autolock on and
off). Check links work and end up in the right place.

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**Definition of Done**:

* [ ] Does this PR satisfy our [Definition of
Done](https://app.asana.com/0/1202500774821704/1207634633537039/f)?

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