Fix typo in reference documentation

Issue: SPR-10171
Backport-Commit: 24cc33306def7aff4aa2c797cd4aea320a4f8523

Conflicts:
	spring-framework-reference/src/overview.xml
Fix broken Castor URLs in ref docs and mapping XML

Issue: SPR-10189
Backport-Commit: d40c8cf

Conflicts:
	spring-framework-reference/src/oxm.xml