Change summary to caption, because summary is obsolete in HTML5 (#7534)

Co-authored-by: Ruben Novelli <rnovelli@redhat.com>

src/main/java/io/reactivex/rxjava3/observers/package-info.java

@@ -20,7 +20,8 @@
  * <p>
  * Available observer variants
  * <br>
- * <table border="1" style="border-collapse: collapse;" summary="The available observer types.">
+ * <table border="1" style="border-collapse: collapse;">
+ * <caption>The available observer types.</caption>
  * <tr><td><b>Reactive type</b></td><td><b>Base interface</b></td><td><b>Simple</b></td><td><b>Disposable</b></td><td><b>Resource</b></td></tr>
  * <tr>
  * <td>{@link io.reactivex.rxjava3.core.Observable Observable}</td>

src/main/java/io/reactivex/rxjava3/subjects/package-info.java

@@ -18,7 +18,8 @@
  * <p>
  * Available subject classes with their respective base classes and consumer interfaces:
  * <br>
- * <table border="1" style="border-collapse: collapse;" summary="The available subject classes with their respective base classes and consumer interfaces.">
+ * <table border="1" style="border-collapse: collapse;">
+ * <caption>The available subject classes with their respective base classes and consumer interfaces.</caption>
  * <tr><td><b>Subject type</b></td><td><b>Base class</b></td><td><b>Consumer interface</b></td></tr>
  * <tr>
  * <td>{@link io.reactivex.rxjava3.subjects.Subject Subject}