[fix][build] Upgrade Conscrypt to 2.6.3 - #26660

Motivation

Conscrypt 2.6.2 was built with a BoringSSL revision that removed X25519Kyber768Draft00 while Conscrypt still configured that group, causing TLS handshakes to fail with Error parsing groups (upstream issue #1530).

The 2.6.3 release notes state that it uses the same Conscrypt source as 2.6.2, rebuilt with BoringSSL 0.20260616.0 to address that regression.

Related: #26659. This upgrade has not been confirmed to resolve the native finalizer crash reported there.

Modifications

• Upgrade conscrypt-openjdk-uber from 2.6.2 to 2.6.3 in the shared version catalog.
• Update the server and shell distribution license inventories to match the bundled JAR version.

Verifying this change

• ./gradlew help quickCheck checkBinaryLicense --configuration-cache
• ./gradlew assemble --configuration-cache
• ./gradlew :pulsar-broker:assemble :pulsar-broker:test --tests org.apache.pulsar.broker.admin.AdminApiTlsAuthTest -PtestRetryCount=0 --configuration-cache — 20 tests passed, no skips or retries.

Validated locally on macOS with Corretto 25. These checks do not establish that the Linux CI crash in #26659 is resolved.

• Make sure that the change passes the CI checks.

Does this pull request potentially affect one of the following parts:

• Dependencies (add or upgrade a dependency)
• The public API
• The schema
• The default values of configurations
• The threading model
• The binary protocol
• The REST endpoints
• The admin CLI options
• The metrics
• Anything that affects deployment