fix: revert podspec git dependency (not allowed by CocoaPods)

CocoaPods doesn't allow :git in podspec files. The git dependency
must be specified in the consuming app's Podfile instead.

For EasyJet integration, they should add to their Podfile:
  pod 'OptimizelySwiftSDK', :git => 'https://github.com/optimizely/swift-sdk.git', :branch => 'fix/upgrade-nwpathmonitor-ios17-requirement'

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: muzahidul-opti

ios/optimizely_flutter_sdk.podspec

@@ -13,7 +13,7 @@ Pod::Spec.new do |s|
   s.source              = { :path => '.' }
   s.source_files        = 'Classes/**/*'
   s.dependency 'Flutter'
-  s.dependency 'OptimizelySwiftSDK', :git => 'https://github.com/optimizely/swift-sdk.git', :branch => 'fix/upgrade-nwpathmonitor-ios17-requirement'
+  s.dependency 'OptimizelySwiftSDK'
   s.platform            = :ios, '10.0'
   # Flutter.framework does not contain a i386 slice.
   s.pod_target_xcconfig = { 'DEFINES_MODULE' => 'YES', 'EXCLUDED_ARCHS[sdk=iphonesimulator*]' => 'i386' }