Auth: Remove deprecated APIs

[paulb777]

Please remove deprecations in public headers in Firebase 7

~/gh4/firebase-ios-sdk/FirebaseAuth/Sources/Public/FirebaseAuth (master) $ git grep -B5 -i deprecat
FIRAuth.h-
FIRAuth.h-/**
FIRAuth.h:    @brief Deprecated. Please directly use email or previousEmail properties instead.
FIRAuth.h-  */
FIRAuth.h-typedef NS_ENUM(NSInteger, FIRActionDataKey) {
FIRAuth.h:  /** Deprecated. Please directly use email property instead.  */
FIRAuth.h-  FIRActionCodeEmailKey = 0,
FIRAuth.h-
FIRAuth.h:  /** Deprecated. Please directly use previousEmail property instead. */
FIRAuth.h-  FIRActionCodeFromEmailKey = 1,
FIRAuth.h-
FIRAuth.h-} NS_SWIFT_NAME(ActionDataKey)
FIRAuth.h:    DEPRECATED_MSG_ATTRIBUTE("Please directly use email or previousEmail properties instead.");
--
FIRAuth.h-    @brief The operation being performed.
FIRAuth.h- */
FIRAuth.h-@property(nonatomic, readonly) FIRActionCodeOperation operation;
FIRAuth.h-
FIRAuth.h-/** @fn dataForKey:
FIRAuth.h:    @brief Deprecated. Please directly use email or previousEmail properties instead.
FIRAuth.h- */
FIRAuth.h-- (NSString *)dataForKey:(FIRActionDataKey)key
FIRAuth.h:    DEPRECATED_MSG_ATTRIBUTE("Please directly use email or previousEmail properties instead.");
--
FIRAuth.h-        fetchSignInMethods(forEmail:completion:) for Swift instead.
FIRAuth.h- */
FIRAuth.h-- (void)fetchProvidersForEmail:(NSString *)email
FIRAuth.h-                    completion:(nullable void (^)(NSArray<NSString *> *_Nullable providers,
FIRAuth.h-                                                  NSError *_Nullable error))completion
FIRAuth.h:    DEPRECATED_MSG_ATTRIBUTE("Please use fetchSignInMethodsForEmail:completion: for Objective-C or "
--
FIRAuth.h- */
FIRAuth.h-- (void)signInAndRetrieveDataWithCredential:(FIRAuthCredential *)credential
FIRAuth.h-                                 completion:
FIRAuth.h-                                     (nullable void (^)(FIRAuthDataResult *_Nullable authResult,
FIRAuth.h-                                                        NSError *_Nullable error))completion
FIRAuth.h:    DEPRECATED_MSG_ATTRIBUTE("Please use signInWithCredential:completion: for Objective-C or "
--
FIRUser.h- */
FIRUser.h-- (void)reauthenticateAndRetrieveDataWithCredential:(FIRAuthCredential *)credential
FIRUser.h-                                         completion:(nullable void (^)(
FIRUser.h-                                                        FIRAuthDataResult *_Nullable authResult,
FIRUser.h-                                                        NSError *_Nullable error))completion
FIRUser.h:    DEPRECATED_MSG_ATTRIBUTE("Please use reauthenticateWithCredential:completion: for"
--
FIRUser.h- */
FIRUser.h-- (void)linkAndRetrieveDataWithCredential:(FIRAuthCredential *)credential
FIRUser.h-                               completion:
FIRUser.h-                                   (nullable void (^)(FIRAuthDataResult *_Nullable authResult,
FIRUser.h-                                                      NSError *_Nullable error))completion
FIRUser.h:    DEPRECATED_MSG_ATTRIBUTE("Please use linkWithCredential:completion: for Objective-C "