chore: update spring boot to version v3.5 to prepare for v4.0 support

[tobixlea]

Issue #, if available:
Upgrading Spring Boot Version
Description of changes:
Update to most recent spring boot v3 version. Final v3 version before release of v4
Version release info
By submitting this pull request

• I confirm that my contribution is made under the terms of the Apache 2.0 license.
• I confirm that I've made a best effort attempt to update all relevant documentation.

[vicheey]

The folder is call -serverless-java-container-springboot3, if we update to springboot 4, shouldn't we have a different folder called aws-serverless-java-container-springboot4 instead?