openresty-debug deb package should not produce resty and restydoc sub-packages

[agentzh]

I've noted that the deb package openresty-debug currently produces the openresty-valgrind-resty and openresty-valgrind-restydoc sub-packages, which is not desired.

Only the openresty package should produce the *-resty and *-restydoc sub-packages.

[dvigueras]

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