various: Consistently switch Java to v11

The latest Jenkins releases support only Java 11 (on the server side, and
thus on the build agent side, as the versions should match).

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
Change-Id: I29fb695171e96dff5dc61d94bdebc0588a2bf577
diff --git a/focal-amd64-mbed-tls-host/Dockerfile b/focal-amd64-mbed-tls-host/Dockerfile
index 847adfa..5c30fa0 100644
--- a/focal-amd64-mbed-tls-host/Dockerfile
+++ b/focal-amd64-mbed-tls-host/Dockerfile
@@ -7,7 +7,7 @@
     git \
     gnupg \
     lsb-release \
-    openjdk-8-jre-headless \
+    openjdk-11-jre-headless \
     openssh-server \
     python3 \
     python3-venv \