debian/control: fix dwz dependency issue

debhelper from buster-backports depends on dwz >= 0.12.20190711.
v2021 has dwz version 0.12-3co1bv2021.0b3. So it results in below
error during package installation,

dpkg: dependency problems prevent configuration of debhelper:
 debhelper depends on dwz (>= 0.12.20190711); however:
  Version of dwz on system is 0.12-3co1bv2021.0b3.

Modify the dwz version in debian/control to fix dependency issues.

Signed-off-by: Vignesh Raman <vignesh.raman@collabora.com>

debian/control

@@ -29,7 +29,7 @@ Depends: autotools-dev,
 # dbgsym support landed in 1.18.0, 1.18.2 fixes a related nasty bug.
          dpkg (>= 1.18.0~),
          dpkg-dev (>= 1.18.2~),
-         dwz (>= 0.12.20190711),
+         dwz (>= 0.12~),
          file (>= 3.23),
          libdpkg-perl (>= 1.17.14),
          man-db,