Update default encoding for feature.xml to UTF-8

[ptziegler]

The feature.xml file has migrated from "ISO-8859-1" to "UTF-8" as default encoding a long time ago. This updates the documentation to reflect this change.

[eclipse-platform-bot]

This pull request changes some projects for the first time in this development cycle.
Therefore the following files need a version increment:

eclipse.platform.releng/features/org.eclipse.help-feature/feature.xml

An additional commit containing all the necessary changes was pushed to the top of this PR's branch. To obtain these changes (for example if you want to push more changes) either fetch from your fork or apply the git patch.

Git patch

From e51c83b1dc83fa654d767b668f3ffd0a46e11009 Mon Sep 17 00:00:00 2001
From: Eclipse Platform Bot <[email protected]>
Date: Mon, 1 Sep 2025 06:07:51 +0000
Subject: [PATCH] Version bump(s) for 4.38 stream


diff --git a/eclipse.platform.releng/features/org.eclipse.help-feature/feature.xml b/eclipse.platform.releng/features/org.eclipse.help-feature/feature.xml
index bae7e9d0a5..18cc7250f9 100644
--- a/eclipse.platform.releng/features/org.eclipse.help-feature/feature.xml
+++ b/eclipse.platform.releng/features/org.eclipse.help-feature/feature.xml
@@ -3,7 +3,7 @@
 <feature
       id="org.eclipse.help"
       label="%featureName"
-      version="2.3.2300.qualifier"
+      version="2.3.2400.qualifier"
       provider-name="%providerName"
       plugin="org.eclipse.help.base"
       license-feature="org.eclipse.license"
-- 
2.51.0

Further information are available in Common Build Issues - Missing version increments.