ios: Proactively bump min iOS version to 14.0, matching zulip-mobile

We could almost certainly bump it to 15, based on the last
platform-version statistics Greg posted, and that was in 2023-09:
  https://chat.zulip.org/#narrow/stream/48-mobile/topic/platform.20versions/near/1648327

But there isn't specific code we want to write for iOS 15 features
right now, so might as well leave that for later.

In fact, I don't think there's a particularly strong need to bump it
to 14, at least at the moment. But there's no reason it needs to lag
behind zulip-mobile. And in case the lower threshold would be an
obstacle later on, it's nice to have it cleared away proactively
ahead of time.

ios/Podfile

@@ -1,4 +1,6 @@
-platform :ios, '12.0'
+# This should match the iOS Deployment Target
+# (in Xcode, that's in project > Runner > Info)
+platform :ios, '14.0'
 
 # CocoaPods analytics sends network stats synchronously affecting flutter build latency.
 ENV['COCOAPODS_DISABLE_STATS'] = 'true'

ios/Podfile.lock

@@ -233,6 +233,6 @@ SPEC CHECKSUMS:
   SwiftyGif: 706c60cf65fa2bc5ee0313beece843c8eb8194d4
   url_launcher_ios: 6116280ddcfe98ab8820085d8d76ae7449447586
 
-PODFILE CHECKSUM: 6998435987a000fdec9b2e1b5b1eef6d54bdba77
+PODFILE CHECKSUM: 7ed5116924b3be7e8fb75f7aada61e057028f5c7
 
 COCOAPODS: 1.13.0

ios/Runner.xcodeproj/project.pbxproj

@@ -344,7 +344,7 @@
 				GCC_WARN_UNINITIALIZED_AUTOS = YES_AGGRESSIVE;
 				GCC_WARN_UNUSED_FUNCTION = YES;
 				GCC_WARN_UNUSED_VARIABLE = YES;
-				IPHONEOS_DEPLOYMENT_TARGET = 12.0;
+				IPHONEOS_DEPLOYMENT_TARGET = 14.0;
 				MTL_ENABLE_DEBUG_INFO = NO;
 				SDKROOT = iphoneos;
 				SUPPORTED_PLATFORMS = iphoneos;
@@ -423,7 +423,7 @@
 				GCC_WARN_UNINITIALIZED_AUTOS = YES_AGGRESSIVE;
 				GCC_WARN_UNUSED_FUNCTION = YES;
 				GCC_WARN_UNUSED_VARIABLE = YES;
-				IPHONEOS_DEPLOYMENT_TARGET = 12.0;
+				IPHONEOS_DEPLOYMENT_TARGET = 14.0;
 				MTL_ENABLE_DEBUG_INFO = YES;
 				ONLY_ACTIVE_ARCH = YES;
 				SDKROOT = iphoneos;
@@ -472,7 +472,7 @@
 				GCC_WARN_UNINITIALIZED_AUTOS = YES_AGGRESSIVE;
 				GCC_WARN_UNUSED_FUNCTION = YES;
 				GCC_WARN_UNUSED_VARIABLE = YES;
-				IPHONEOS_DEPLOYMENT_TARGET = 12.0;
+				IPHONEOS_DEPLOYMENT_TARGET = 14.0;
 				MTL_ENABLE_DEBUG_INFO = NO;
 				SDKROOT = iphoneos;
 				SUPPORTED_PLATFORMS = iphoneos;