Avoid using yum (which requires http:// access) in launch script tests

Fixes gh-26240

spring-boot-tests/spring-boot-integration-tests/spring-boot-launch-script-tests/src/intTest/resources/conf/CentOS/7.9-e4ca2ed0/Dockerfile

 # CentOS 7.9 from 18/11/2020
 FROM centos@sha256:e4ca2ed0202e76be184e75fb26d14bf974193579039d5573fb2348664deef76e
-RUN yum install -y wget && \
-    yum install -y curl && \
-    wget --output-document jdk.rpm \
-        https://cdn.azul.com/zulu/bin/zulu8.21.0.1-jdk8.0.131-linux.x86_64.rpm && \
-    yum --nogpg localinstall -y jdk.rpm && \
-    rm -f jdk.rpm
+RUN mkdir -p /opt/openjdk && \
+    cd /opt/openjdk && \
+    curl -L https://github.com/AdoptOpenJDK/openjdk8-binaries/releases/download/jdk8u202-b08/OpenJDK8U-jdk_x64_linux_hotspot_8u202b08.tar.gz | tar zx --strip-components=1
+ENV JAVA_HOME /opt/openjdk
+ENV PATH $JAVA_HOME/bin:$PATH