[releng] Switch to Spring Boot 2.3.1
[releng] Switch to Spring Boot 2.3.1

Signed-off-by: Stéphane Bégaudeau <fa7070c1dfe48b69ae467d915a7a33333baf63a2@gmail.com>
svalyn/svalyn,svalyn/svalyn,svalyn/svalyn,svalyn/svalyn