DynamicLink initializer shouldn't be available from Swift

[ryanwilson]

There's no init marked as NS_UNAVAILABLE, so a bare initializer is currently available in Swift but shouldn't be.

firebase-ios-sdk/FirebaseDynamicLinks/Sources/Public/FirebaseDynamicLinks/FIRDynamicLink.h

Lines 55 to 86 in 8467858

	NS_SWIFT_NAME(DynamicLink)
	@interface FIRDynamicLink : NSObject
	/**
	* @property url
	* @abstract The URL that was passed to the app.
	*/
	@property(nonatomic, copy, readonly, nullable) NSURL *url;
	/**
	* @property matchType
	* @abstract The match type of the received Dynamic Link.
	*/
	@property(nonatomic, assign, readonly) FIRDLMatchType matchType;
	/**
	* @property utmParametersDictionary
	* @abstract UTM parameters associated with a Firebase Dynamic Link.
	*/
	@property(nonatomic, copy, readonly) NSDictionary<NSString *, id> *utmParametersDictionary;
	/**
	* @property minimumAppVersion
	* @abstract The minimum iOS application version that supports the Dynamic Link. This is retrieved
	* from the imv= parameter of the Dynamic Link URL. Note: This is not the minimum iOS system
	* version, but the minimum app version. If app version of the opening app is less than the
	* value of this property, then app expected to open AppStore to allow user to download most
	* recent version. App can notify or ask user before opening AppStore.
	*/
	@property(nonatomic, copy, readonly, nullable) NSString *minimumAppVersion;
	@end

We'll need to determine the right strategy for this: it's a breaking change to remove it, but it doesn't work as is. Introducing an initializer that's deprecated will introduce the API for ObjC users, which we don't want either.

[andrewheard]

Note: this API is also available for ObjC users

FIRDynamicLink *dynamicLink = [[FIRDynamicLink alloc] init];