fix(shorebird_cli): fix export-method parsing in release ios command

[bryanoltman]

Description

This was previously checking export-method for enum name instead of arg name (so adHoc was expected instead of ad-hoc.

Fixes #1708.

Type of Change

• ✨ New feature (non-breaking change which adds functionality)
• 🛠️ Bug fix (non-breaking change which fixes an issue)
• ❌ Breaking change (fix or feature that would cause existing functionality to change)
• 🧹 Code refactor
• ✅ Build configuration change
• 📝 Documentation
• 🗑️ Chore

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (0a63a3c) 100.00% compared to head (b73292c) 100.00%.

Additional details and impacted files

@@            Coverage Diff            @@
##              main     #1710   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          158       158           
  Lines         5006      5007    +1     
=========================================
+ Hits          5006      5007    +1     

Flag	Coverage Δ
shorebird_cli	100.00% <100.00%> (ø)

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