Restore indentation in published spring-boot-starter-parent pom

Closes gh-16466

spring-boot-project/spring-boot-starters/spring-boot-starter-parent/src/main/xslt/post-process-flattened-pom.xsl

@@ -3,7 +3,7 @@
 	xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:m="http://maven.apache.org/POM/4.0.0"
 	exclude-result-prefixes="m">
 	<xsl:output method="xml" encoding="utf-8" indent="yes"
-		xslt:indent-amount="4" xmlns:xslt="https://xml.apache.org/xslt" />
+		xslt:indent-amount="2" xmlns:xslt="http://xml.apache.org/xslt" />
 	<xsl:strip-space elements="*" />
 	<xsl:template match="@*|node()">
 		<xsl:copy>