/etc/apache2/mods-available/disk_cache.load is in apache2.2-common 2.2.22-13+deb7u6.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 | # Depends: cache
LoadModule disk_cache_module /usr/lib/apache2/modules/mod_disk_cache.so
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