Drop dependencies.

These build dependencies is pulled in either way, so there no need to mention them
explicitly.

debian/control

@@ -5,7 +5,6 @@ Section: python
 Priority: optional
 Build-Depends: debhelper-compat (= 13),
                dh-python,
-               dpkg-dev (>= 1.17.14),
                python-agate-doc <!nodoc>,
                python3-agate <!nocheck> <!nodoc>,
                python3-all,
@@ -16,7 +15,6 @@ Build-Depends: debhelper-compat (= 13),
                python3-sphinx <!nodoc>,
                python3-sphinx-rtd-theme <!nodoc>,
                python3-xlrd <!nocheck> <!nodoc>,
-               sphinx-common
 Standards-Version: 4.6.0
 Vcs-Browser: https://salsa.debian.org/python-team/packages/python-agate-excel
 Vcs-Git: https://salsa.debian.org/python-team/packages/python-agate-excel.git