fix: wrong return in javadocs for bookmeta (#5579)

Closes #5574.
Reviewed-by: Mariell Hoversholm <proximyst@proximyst.com>

Spigot-API-Patches/Adventure.patch

@@ -3273,6 +3273,7 @@ index 0000000000000000000000000000000000000000..00000000000000000000000000000000
  import net.md_5.bungee.api.chat.BaseComponent;
  import org.bukkit.Material;
 +import org.checkerframework.checker.nullness.qual.NonNull;
++import org.checkerframework.common.returnsreceiver.qual.This;
  import org.jetbrains.annotations.NotNull;
  import org.jetbrains.annotations.Nullable;
  
@@ -3308,11 +3309,11 @@ index 0000000000000000000000000000000000000000..00000000000000000000000000000000
 +     * Limited to 32 characters. Removes title when given null.
 +     *
 +     * @param title the title to set
-+     * @return true if the title was successfully set
++     * @return the same {@link BookMeta} instance
 +     */
 +    @NotNull
 +    @Override
-+    BookMeta title(@Nullable net.kyori.adventure.text.Component title);
++    @This BookMeta title(@Nullable net.kyori.adventure.text.Component title);
 +
 +    /**
 +     * Gets the author of the book.
@@ -3330,10 +3331,11 @@ index 0000000000000000000000000000000000000000..00000000000000000000000000000000
 +     * Sets the author of the book. Removes author when given null.
 +     *
 +     * @param author the author to set
++     * @return the same {@link BookMeta} instance
 +     */
 +    @NotNull
 +    @Override
-+    BookMeta author(@Nullable net.kyori.adventure.text.Component author);
++    @This BookMeta author(@Nullable net.kyori.adventure.text.Component author);
 +    /**
 +     * Gets the specified page in the book. The page must exist.
 +     * <p>