AppCheck javadoc nits (#2621)

* AppCheck javadoc nits

* Fix formatting error

Author: kevinthecheung

appcheck/firebase-appcheck/src/main/java/com/google/firebase/appcheck/AppCheckProvider.java

@@ -20,8 +20,8 @@
 /**
  * Interface for a provider that generates {@link AppCheckToken}s. This provider can be called at
  * any time by any Firebase library that depends (optionally or otherwise) on {@link
- * AppCheckToken}s. This provider should be responsible for determining if a new token can be
- * created at the time of the call and returning that new token if it can be.
+ * AppCheckToken}s. This provider is responsible for determining if it can create a new token at the
+ * time of the call and returning that new token if it can.
  */
 public interface AppCheckProvider {
 

appcheck/firebase-appcheck/src/main/java/com/google/firebase/appcheck/FirebaseAppCheck.java

@@ -37,9 +37,9 @@ public static FirebaseAppCheck getInstance(@NonNull FirebaseApp firebaseApp) {
   }
 
   /**
-   * Installs the given {@link AppCheckProviderFactory}, overwriting any that previously was
+   * Installs the given {@link AppCheckProviderFactory}, overwriting any that were previously
    * associated with this FirebaseAppCheck instance. Any {@link AppCheckTokenListener}s attached to
-   * this FirebaseAppCheck instance will be transferred from any existing factory to the newly
+   * this FirebaseAppCheck instance will be transferred from existing factories to the newly
    * installed one.
    *
    * <p>Automatic token refreshing will only occur if the global {@code
@@ -52,9 +52,9 @@ public static FirebaseAppCheck getInstance(@NonNull FirebaseApp firebaseApp) {
   public abstract void installAppCheckProviderFactory(@NonNull AppCheckProviderFactory factory);
 
   /**
-   * Installs the given {@link AppCheckProviderFactory}, overwriting any that previously was
+   * Installs the given {@link AppCheckProviderFactory}, overwriting any that were previously
    * associated with this FirebaseAppCheck instance. Any {@link AppCheckTokenListener}s attached to
-   * this FirebaseAppCheck instance will be transferred from any existing factory to the newly
+   * this FirebaseAppCheck instance will be transferred from existing factories to the newly
    * installed one.
    *
    * <p>Automatic token refreshing will only occur if the {@code isTokenAutoRefreshEnabled} field is