Add gradle upgrade notes

Author: jdaugherty

UPGRADE7.md

@@ -6,6 +6,10 @@ Experienced while upgrading modules for Grails 7
   - https://github.com/grails/gorm-hibernate5/pull/910/commits/c8de45df204966ccc228b46b94beeb2142ae0f59 
 - [GROOVY-10621](https://issues.apache.org/jira/browse/GROOVY-10621) 
   - Primitive booleans will no longer generate the form of isProperty & getProperty.  They will only generate isProperty()
+- The amount of boilerplate required in gradle files has been reduced:  
+  - When `org.grails.grails-plugin` gradle plugin is applied, the bootJar task is disabled by default.  No more needing to explicitly set it to false!
+  - We no longer have a `micronaut-bom` and a `spring-bom`.  We only have the `spring-bom` now, which allows `grails-bom` to inherit from it and be applied as part of the Spring Dependency Management plugin.  This means versions do not need included for any library in the bom.  Override bom versions via gradle properties.
+  - The `grailsPublish` plugin returns and is no longer an internal only plugin.  It has been enhanced to work with some multi-project workflows.  Eliminate publishing boilerplate of the nexus-publish, maven-publish, & signing plugin by adopting it.
 - Jar artifacts produced by Grails Plugins will no longer have the suffix `-plain`
   - https://github.com/grails/grails-gradle-plugin/pull/347
 - [GROOVY-5169](https://issues.apache.org/jira/browse/GROOVY-5169)  [GROOVY-10449](https://issues.apache.org/jira/browse/GROOVY-10449)