Prepare for Spring Security 6.2

[jzheaux]

• Update SecurityNamespaceHandler to require 6.2
• Add spring-security-6.2.rnc and spring-security-6.2.xsd
• Update spring.schemas; add lines for spring-security-6.2.xsd and change the setting for spring-security.xsd to point to spring-security-6.2.xsd
• Point spring-security.xsd symlink to spring-security-6.2.xsd
• Update XsdDocumentedTests to point to 6.2
• Increment schema count in XsdDocumentedTests
• Update SpringSecurityCoreVersion to 620L
• Update RNC link in docs/modules/ROOT/pages/servlet/appendix/namespace/index.adoc
• Update What's New to an empty 6.2 section
• Update prepare-forward-merge to point to 6.2.x
• Update gradle.properties version to 6.2.0-SNAPSHOT
• Update security.tld tlib-version to 6.2
• Update Dependabot configuration
• Update release-scheduler.yml

[jzheaux]

Closed in fb910e2

[marcusdacoregio]

@jzheaux I also added "Update Dependabot configuration" to the list

[sjohnr]

@jzheaux I also added "Update release-scheduler.yml" to the list.