Fix broken documentation found while reviewing C# docs. (#670)

Author: wilhuff

firebase-firestore/src/main/java/com/google/firebase/firestore/DocumentSnapshot.java

@@ -38,7 +38,7 @@
 
 /**
  * A {@code DocumentSnapshot} contains data read from a document in your Cloud Firestore database.
- * The data can be extracted with the {@link #getData()} or {@link #get()} methods.
+ * The data can be extracted with the {@link #getData()} or {@link #get(String)} methods.
  *
  * <p>If the {@code DocumentSnapshot} points to a non-existing document, {@link #getData()} and its
  * corresponding methods will return {@code null}. You can always explicitly check for a document's

firebase-firestore/src/main/java/com/google/firebase/firestore/QuerySnapshot.java

@@ -82,7 +82,7 @@ public Query getQuery() {
     return originalQuery;
   }
 
-  /** @return The metadata for this document snapshot. */
+  /** @return The metadata for this query snapshot. */
   @NonNull
   public SnapshotMetadata getMetadata() {
     return metadata;

firebase-firestore/src/main/java/com/google/firebase/firestore/SetOptions.java

@@ -67,8 +67,8 @@ public static SetOptions merge() {
   }
 
   /**
-   * Changes the behavior of {@code set()} calls to only replace the fields under fieldPaths. Any
-   * field that is not specified in fieldPaths is ignored and remains untouched.
+   * Changes the behavior of {@code set()} calls to only replace the given fields. Any field that is
+   * not specified in {@code fields} is ignored and remains untouched.
    *
    * <p>It is an error to pass a {@code SetOptions} object to a {@code set()} call that is missing a
    * value for any of the fields specified here.
@@ -88,8 +88,8 @@ public static SetOptions mergeFields(@NonNull List<String> fields) {
   }
 
   /**
-   * Changes the behavior of {@code set()} calls to only replace the fields under fieldPaths. Any
-   * field that is not specified in fieldPaths is ignored and remains untouched.
+   * Changes the behavior of {@code set()} calls to only replace the given fields. Any field that is
+   * not specified in {@code fields} is ignored and remains untouched.
    *
    * <p>It is an error to pass a {@code SetOptions} object to a {@code set()} call that is missing a
    * value for any of the fields specified here.
@@ -109,8 +109,8 @@ public static SetOptions mergeFields(String... fields) {
   }
 
   /**
-   * Changes the behavior of {@code set()} calls to only replace the fields under fieldPaths. Any
-   * field that is not specified in fieldPaths is ignored and remains untouched.
+   * Changes the behavior of {@code set()} calls to only replace the given fields. Any field that is
+   * not specified in {@code fields} is ignored and remains untouched.
    *
    * <p>It is an error to pass a {@code SetOptions} object to a {@code set()} call that is missing a
    * value for any of the fields specified here in its to data argument.