Convert obj-c and swift pattern to str

[changusmc]

The pattern is currently a bytestring, and the app is failing to compile

pattern:@"b"^['&A-Za-z0-9._%+-]+@[A-Za-z0-9-][A-Za-z0-9.-]*\\\\.[A-Za-z]{2,15}$"

Checklist

General Contributing

• Have you read the Code of Conduct and signed the CLA?

Is This a Code Change?

• [] Non-code related change (markdown/git settings etc)
• Code Change
• Example/Test Code Change

Validation

• Have you ran tox?
• Do the tests pass?

[codecov]

Codecov Report

Merging #204 (0922df3) into main (27a566a) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #204   +/-   ##
=======================================
  Coverage   51.72%   51.72%           
=======================================
  Files          37       37           
  Lines        8369     8369           
  Branches     1786     1786           
=======================================
  Hits         4329     4329           
  Misses       3726     3726           
  Partials      314      314           

Flag	Coverage Δ
unit	51.72% <ø> (ø)

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Impacted Files	Coverage Δ
stone/backends/obj_c_types.py	0.00% <ø> (ø)
stone/backends/swift_types.py	0.00% <ø> (ø)

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