Fix small typos in public documentation. (#2192)

Author: ryanwilson

Firebase/Auth/Source/Public/FIRAuthTokenResult.h

@@ -49,7 +49,7 @@ NS_SWIFT_NAME(AuthTokenResult)
 
 /** @property signInProvider
     @brief Stores sign-in provider through which the token was obtained.
-    @remarks This does not necesssarily map to provider IDs.
+    @remarks This does not necessarily map to provider IDs.
  */
 @property (nonatomic, readonly) NSString *signInProvider;
 

Firebase/Auth/Source/Public/FIRPhoneAuthProvider.h

@@ -61,7 +61,7 @@ NS_SWIFT_NAME(PhoneAuthProvider)
 + (instancetype)providerWithAuth:(FIRAuth *)auth NS_SWIFT_NAME(provider(auth:));
 
 /** @fn verifyPhoneNumber:UIDelegate:completion:
-    @brief Starts the phone number authentication flow by sending a verifcation code to the
+    @brief Starts the phone number authentication flow by sending a verification code to the
         specified phone number.
     @param phoneNumber The phone number to be verified.
     @param UIDelegate An object used to present the SFSafariViewController. The object is retained

Firebase/Database/Public/FIRDatabaseQuery.h

@@ -22,8 +22,8 @@ NS_ASSUME_NONNULL_BEGIN
 
 /**
  * A FIRDatabaseHandle is used to identify listeners of Firebase Database events. These handles
- * are returned by observeEventType: and and can later be passed to removeObserverWithHandle: to
- * stop receiving updates.
+ * are returned by observeEventType: and can later be passed to removeObserverWithHandle: to stop
+ * receiving updates.
  */
 typedef NSUInteger FIRDatabaseHandle NS_SWIFT_NAME(DatabaseHandle);