Fix typo in AvoidUsingPlainTextForPassword error message: 'to' being repeated two times

[ALiwoto]

PR Summary

This pull request fixes a small typo in Strings.resx file whereas to in value of AvoidUsingPlainTextForPasswordError was being repeated two times.

PR Checklist

• [x] PR has a meaningful title
  • Use the present tense and imperative mood when describing your changes
• [x] Summarized changes
• [x] Change is not breaking
• [x] Make sure all .cs, .ps1 and .psm1 files have the correct copyright header
• [x] Make sure you've added a new test if existing tests do not effectively test the code changed and/or updated documentation
• [x] This PR is ready to merge and is not [Work in Progress]