setup.py: remove unnecessary requirement on safe-netrc

this is a first-class requirement of igwn-auth-utils now

ligo-gracedb.spec

@@ -37,7 +37,6 @@ Requires: python%{python3_pkgversion}-future
 Requires: python%{python3_pkgversion}-igwn-auth-utils
 Requires: python%{python3_pkgversion}-requests
 Requires: python%{python3_pkgversion}-six
-Requires: python%{python3_pkgversion}-safe-netrc
 %{?python_provide:%python_provide python%{python3_pkgversion}-%{srcname}}
 %description -n python%{python3_pkgversion}-%{srcname}
 The gravitational-wave candidate event database (GraceDB) is a

setup.py

@@ -103,7 +103,6 @@ setup(
                       'cryptography>=1.7.2, <=36.0.2',
                       'requests>=2.6.0',
                       'igwn-auth-utils>=0.3.1',
-                      'safe_netrc>=1.0.0',
                       ],
     setup_requires=SETUP_REQUIRES,
     tests_require=TEST_REQUIRES,