Drop remaining references to LGPL-3 libdw

In order to be consist with the decision of removing libdw drop remaining
references to it.

Signed-off-by: Walter Lozano <walter.lozano@collabora.com>

debian/control

@@ -62,7 +62,7 @@ Depends: libgstreamer1.0-0 (= ${binary:Version}),
          pkg-config,
          libglib2.0-dev,
          libunwind-dev [i386 amd64 armel armhf arm64 powerpc ppc64 ppc64el mipsel mips64el],
-         libdw-dev [i386 amd64 armel armhf arm64 powerpc ppc64 ppc64el mipsel mips64el],
+#         libdw-dev [i386 amd64 armel armhf arm64 powerpc ppc64 ppc64el mipsel mips64el], # LGPL-3
          ${shlibs:Depends},
          ${misc:Depends},
          gir1.2-gstreamer-1.0 (= ${binary:Version})