Upgrade mvnw to 3.10.x #1189

CI now uses mvnw instead of the bundled mvn CLI to align versions.
Publishing started failing with maven 3.10, see https://github.com/modelcontextprotocol/java-sdk/actions/runs/38772171258

TL;DR: With Maven 3.10.0, the staging metadata in target/central-staging is written as
maven-metadata-local.xml. central-publishing-maven-plugin 0.7.0 only removes
maven-metadata-central-staging.xml before bundling, so the leftover files end up in the
bundle and Central rejects the deployment:

Deployment <id> failed
common:
 - Bundle has content that does NOT have a .pom file: io/modelcontextprotocol/sdk/mcp-core, io/modelcontextprotocol/sdk/mcp, ...