[SPARK-55489] Update extended LTS period post SPIP ratification

Regenerated with docker container.
<img width="3584" height="1366" alt="image" src="https://github.com/user-attachments/assets/9d9f15c4-c9dd-45f3-b803-f1bd84ccbebb" />

Author: Holden Karau <holden@pigscanfly.ca>

Closes #682 from holdenk/SPARK-LTS-SPARK-55489.

Author: holdenk

site/versioning-policy.html

@@ -310,7 +310,9 @@ <h2>Maintenance releases and EOL</h2>
 of 2.3.0 in February 2018. No more 2.3.x releases should be expected after that point, even for bug fixes.</p>
 
 <p>The last minor release within a major release will typically be maintained for longer as an &#8220;LTS&#8221; release.
-For example, 3.5.0 was released on September 13th 2023 and will be maintained for 31 months until April 12th 2026.</p>
+For example, 3.5.0 was released on September 13th 2023 and would normally be maintained for 31 months until April 12th 2026.</p>
+
+<p>As an exception from the normal versioning policy, version 3.5.x has an &#8220;extended&#8221; LTS period to allow for migrations to be completed. This extended LTS period will end <em>November 2027</em>. During the 3.5.x extended LTS period, we will only include security fixes. This extend LTS only applies to the primary Apache Spark project/repo and does not apply to sub projects with separate repos/releases (namely: Spark Connect for Swift/Rust/Go and Spark Kubernetes operator). Additionally, as Java 8 support may be removed from other projects (including Hadoop), should a dependency have a security fix that is not backported to a Java 8 compatible version we may decide to mark that vulnerability as a won&#8217;t fix or release the new version without Java 8 support.</p>
 
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versioning-policy.md

@@ -115,4 +115,6 @@ For example, branch 2.3.x is no longer considered maintained as of September 201
 of 2.3.0 in February 2018. No more 2.3.x releases should be expected after that point, even for bug fixes.
 
 The last minor release within a major release will typically be maintained for longer as an "LTS" release.
-For example, 3.5.0 was released on September 13th 2023 and will be maintained for 31 months until April 12th 2026.
+For example, 3.5.0 was released on September 13th 2023 and would normally be maintained for 31 months until April 12th 2026.
+
+As an exception from the normal versioning policy, version 3.5.x has an "extended" LTS period to allow for migrations to be completed. This extended LTS period will end *November 2027*. During the 3.5.x extended LTS period, we will only include security fixes. This extend LTS only applies to the primary Apache Spark project/repo and does not apply to sub projects with separate repos/releases (namely: Spark Connect for Swift/Rust/Go and Spark Kubernetes operator). Additionally, as Java 8 support may be removed from other projects (including Hadoop), should a dependency have a security fix that is not backported to a Java 8 compatible version we may decide to mark that vulnerability as a won't fix or release the new version without Java 8 support.