git: openjdk/jfx: master: 8263759: Update boot JDK to 15.0.2

[Kevin Rushforth]

Changeset: e23a2feb
Author:    Kevin Rushforth <kcr at openjdk.org>
Date:      2021-03-18 15:05:04 +0000
URL:       https://git.openjdk.java.net/jfx/commit/e23a2feb

8263759: Update boot JDK to 15.0.2

Reviewed-by: jvos

! .github/workflows/submit.yml
! build.properties