[openjdk-25, master] d/rules: fix dangling symlinks

• Security Manager was removed in -25, so the JDK image no longer has default.policy and java.policy.
• jaxp-strict.properties.template was moved by d/rules to jaxp-strict.properties, but we still created symlink to jaxp-strict.properties.template. Replace mv with cp so that link to jaxp-strict.properties.template is not broken.

Changes:

  * d/rules: fix dangling symlinks
    - drop lib/security/default.policy.
    - do not move jaxp-strict.properties.template
    - drop conf/security/java.policy

Testing:

• rebuild in sid chroot, install all binary packages, run

$ find /usr/lib/jvm/java-25-openjdk-amd64 -type l ! -exec test -e {} \; -print
$

No broken symlinks found.