Replace usages of @aws-sdk/util-utf8-browser with @aws-sdk/util-utf8

[trivikr]

Is your feature request related to a problem? Please describe.

The @aws-sdk/util-utf8-browser packages are deprecated in v3, as the code is merged in a new package @aws-sdk/util-utf8
PR for reference: aws/aws-sdk-js-v3#4372

Some packages in aws-sdk-js-crypto-helpers depend on @aws-sdk/util-utf8-browser
Code search link: https://github.com/search?q=repo%3Aaws%2Faws-sdk-js-crypto-helpers%20util-utf8-browser&type=code

Describe the solution you'd like

Replace usages of @aws-sdk/util-utf8-browser with @aws-sdk/util-utf8 and release 3.1.0

Describe alternatives you've considered

Continue using deprecated module @aws-sdk/util-utf8-browser