it didn't work, we still got setuptools_scm 6.3.2, maybe putting it first helps

setup.cfg

@@ -41,7 +41,6 @@ install_requires =
     # incompatible with Tahoe-LAFS'.  So duplicate them here (the ones that
     # have been observed to cause problems).
     Twisted[tls,conch] >= 19.10.0
-    tahoe-lafs >=1.17,<1.18
 
     # Tahoe-LAFS 1.17 adds a cbor2 dependency; cbor2 has a setuptools_scm
     # dependency; setuptools_scm has dropped Python 2 support without
@@ -49,6 +48,8 @@ install_requires =
     # here to avoid getting a broken version.
     setuptools_scm < 6
 
+    tahoe-lafs >=1.17,<1.18
+
     treq
     pyutil
     prometheus-client