Deb: Don't define libzstd1 or other libraries as install dependencies manually

If something was built using a build dependency, it will automatically
be a install dependency via ${shlibs:Depends}, so no need to define it
manually.

This also fixes a bug related to a over autobake-deb.sh mangling
the control file architecture field on Trusty and Jessie.

debian/control

@@ -562,8 +562,7 @@ Description: Connect storage engine for MariaDB
 
 Package: mariadb-plugin-rocksdb
 Architecture: amd64 arm64 mips64el ppc64el
-Depends: libzstd1,
-         mariadb-server-10.4 (= ${binary:Version}),
+Depends: mariadb-server-10.4 (= ${binary:Version}),
          ${misc:Depends},
          ${shlibs:Depends}
 Breaks: mariadb-rocksdb-engine-10.2,