remove unnecessary setting to empty string

[jhendrixMSFT]

• The purpose of this PR is explained in this or a referenced issue.
• The PR does not update generated files.
  • These files are managed by the codegen framework at Azure/autorest.go.
• Tests are included and/or updated for code changes.
• Updates to CHANGELOG.md are included.
• MIT license headers are included in each file.

[antkmsft]

The reason it was there is that at a time, codegen was generating pagers in old format, and this code was borrowed from keyvault. Now that the new pattern is applied everywhere, it makes sense for all pagers to look the same. I.e. there wasn't any special meaning behind this condition, other that doing what we were doing in other places.

[antkmsft]

Thank you!