Remove Java 21 on Ubuntu 26

The native package should now be able to correctly
detect and manage Java 25 without failing.

Change-Id: I9200ebe8a4d4d1b4c9035355da664ced903eb9ec

almalinux/10/Dockerfile

diff --git a/almalinux/10/Dockerfile b/almalinux/10/Dockerfile
index c33749d..d44fce9 100644
--- a/almalinux/10/Dockerfile
+++ b/almalinux/10/Dockerfile
@@ -12,7 +12,7 @@
 # Install OS pre-prequisites, OpenJDK and Gerrit in two subsequent transactions
 # (pre-trans Gerrit script needs to have access to the Java command)
 RUN yum -y install initscripts && \
-    yum -y install java-21-openjdk
+    yum -y install java-25-openjdk
 
 RUN yum -y install gerrit-3.15.0-0rc0 && \
     /entrypoint.sh init && \

ubuntu/26/Dockerfile

diff --git a/ubuntu/26/Dockerfile b/ubuntu/26/Dockerfile
index b4de301..7c907b0 100644
--- a/ubuntu/26/Dockerfile
+++ b/ubuntu/26/Dockerfile
@@ -15,10 +15,9 @@
 
 ADD entrypoint.sh /
 
-RUN apt-get -y install openjdk-21-jdk && \
-    apt-get -y upgrade && \
+RUN apt-get -y upgrade && \
+    apt-get -y install openjdk-25-jdk && \
     apt-get -y install gerrit=3.15.0-0rc0 && \
-    apt-get -y remove openjdk-21-jdk && \
     apt-mark hold gerrit && \
     /entrypoint.sh init && \
     bash -c 'rm -f /var/gerrit/etc/{ssh,secure}* && rm -Rf /var/gerrit/{static,index,logs,data,index,cache,git,db,tmp}/*' && \