fix: `Parse.setServer` does not set new server URL

[mtrezza]

New Pull Request Checklist

• [x] I am not disclosing a vulnerability.
• [x] I am creating this PR in reference to an issue.

Issue Description

Closes: https://github.com/parse-community/Parse-SDK-iOS-OSX/issues/1528

Approach

• Remove unused PFInternalUtils.setParseServer
• Completely re-init SDK when setting new server URL

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[parseplatformorg]

🎉 This change has been released in version 2.0.3