docs: fix javadoc errors (#1126)

* docs: fix javadoc errors

* fix

* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

* more fixes

---------

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

Author: kolea2

google-cloud-datastore/src/main/java/com/google/cloud/datastore/AggregationQuery.java

@@ -45,7 +45,7 @@
  * }
  * }</pre>
  *
- * <h4>{@link GqlQuery} example:</h4>
+ * <p>{@link GqlQuery} example:
  *
  * <pre>{@code
  * GqlQuery<?> selectAllGqlQuery = Query.newGqlQueryBuilder(

google-cloud-datastore/src/main/java/com/google/cloud/datastore/AggregationResults.java

@@ -24,10 +24,10 @@
 import java.util.Objects;
 
 /**
- * The result of an {@link AggregationQuery} query submission. Contains a {@link
- * List<AggregationResult>} and readTime {@link Timestamp} in it.
+ * The result of an {@link AggregationQuery} query submission. Contains a List&lt;{@link
+ * AggregationResult}&gt; and readTime {@link Timestamp} in it.
  *
- * <p>This can be used to iterate over an underlying {@link List<AggregationResult>} directly.
+ * <p>This can be used to iterate over an underlying List&lt;{@link AggregationResult}&gt; directly.
  */
 public class AggregationResults implements Iterable<AggregationResult> {
 
@@ -41,7 +41,7 @@ public AggregationResults(List<AggregationResult> aggregationResults, Timestamp
     this.readTime = readTime;
   }
 
-  /** Returns {@link Iterator} for underlying {@link List<AggregationResult>}. */
+  /** Returns {@link Iterator} for underlying List&lt;{@link AggregationResult}&gt;. */
   @Override
   public Iterator<AggregationResult> iterator() {
     return this.aggregationResults.iterator();

google-cloud-datastore/src/main/java/com/google/cloud/datastore/Datastore.java

@@ -484,7 +484,7 @@ interface TransactionCallable<T> {
    * }
    * }</pre>
    *
-   * <h4>{@link GqlQuery} example:</h4>
+   * <p>{@link GqlQuery} example:
    *
    * <pre>{@code
    * GqlQuery<?> selectAllGqlQuery = Query.newGqlQueryBuilder(

google-cloud-datastore/src/main/java/com/google/cloud/datastore/GqlQuery.java

@@ -41,7 +41,7 @@
 /**
  * A Google Cloud Datastore GQL query.
  *
- * <h3>A usage example:</h3>
+ * <p>A usage example:
  *
  * <p>When the type of the results is known the preferred usage would be:
  *

google-cloud-datastore/src/main/java/com/google/cloud/datastore/Query.java

@@ -274,7 +274,7 @@ public static ProjectionEntityQuery.Builder newProjectionEntityQueryBuilder() {
    * // Use aggregationResults
    * }</pre>
    *
-   * <h4>{@link GqlQuery} example:</h4>
+   * <p>{@link GqlQuery} example:
    *
    * <pre>{@code
    * GqlQuery<?> selectAllGqlQuery = Query.newGqlQueryBuilder(

google-cloud-datastore/src/main/java/com/google/cloud/datastore/StructuredQuery.java

@@ -46,7 +46,7 @@
  * An implementation of a Google Cloud Datastore Query that can be constructed by providing all the
  * specific query elements.
  *
- * <h3>A usage example:</h3>
+ * <p>A usage example:
  *
  * <p>A simple query that returns all entities for a specific kind
  *