Add online help for removeLastBuild option

Author: AmoghParmar

core/src/main/resources/hudson/tasks/LogRotator/help-removeLastBuild.html

@@ -0,0 +1,24 @@
+<div>
+  <p>
+    When enabled, Jenkins is allowed to remove the <b>last successful</b> and
+    <b>last stable</b> build if they match the configured build discarder rules.
+  </p>
+
+  <p>
+    By default, Jenkins keeps the most recent successful and stable builds,
+    even if they are older than the configured retention limits.
+    Enabling this option overrides that behavior.
+  </p>
+
+  <p>
+    <b>Example:</b><br/>
+    If builds are configured to be deleted after 7 days, and the most recent
+    successful build is 30 days old, it will normally be kept.
+    With this option enabled, that build will also be removed.
+  </p>
+
+  <p>
+    This option is also available in Pipelines using the
+    <code>buildDiscarder(logRotator(..., removeLastBuild: true))</code> syntax.
+  </p>
+</div>