d/patches: drop unused patches

d/patches: drop unused patches

with commit 426b8f0a33327cafbb4597ad9c8343b4aa890ed5 we use debhelper
for building, and I missed that the dpkg-buildpackage invocation for
building binary packages only does not prepare the source (by applying
quilt-patches)

Since no regressions for the accidental change were reported both
patches seem unneccessary:
disable-dkim.patch - our users do use DKIM and adapt rules which rely
on it - so it does not seem appropriate to not load the module anymore
(patch was introduced before PMG 5.0)
avoid-init.pre-update.patch: this was addressed differently by
d27e5c832e0188a71b2d416de95e19b348072755

noticed while trying to build the dsc target

Signed-off-by: Stoiko Ivanov <s.ivanov@proxmox.com>
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>