[3006.x] Fix stdin raw newlines for timed subprocess

[niklasr22]

What does this PR do?

What issues does this PR fix or reference?

Fixes issue #62501

Previous Behavior

The following error was thrown when running cmd.run with a str passed via stdin and stdin_raw_newlines=True

Passed invalid arguments to cmd.run: memoryview: a bytes-like object is required, not 'str'

New Behavior

String also gets converted to bytes when stdin_raw_newlines=True, so no error is thrown

Merge requirements satisfied?

[NOTICE] Bug fixes or features added to Salt require tests.

• [x] Docs
• [x] Changelog - https://docs.saltproject.io/en/master/topics/development/changelog.html
• [x] Tests written/updated

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Yes

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