fix(ios): add missing MinimumOSVersion to AppFrameworkInfo.plist

App Store validation rejected the IPA because App.framework's Info.plist
lacked the required MinimumOSVersion key, set to 14.0 to match the project's IPHONEOS_DEPLOYMENT_TARGET.

Author: ericgriffin

ios/Flutter/AppFrameworkInfo.plist

@@ -20,5 +20,7 @@
   <string>????</string>
   <key>CFBundleVersion</key>
   <string>1.0</string>
+  <key>MinimumOSVersion</key>
+  <string>14.0</string>
 </dict>
 </plist>