build: Move constraints file to project root.

Author: seifertm

.github/dependabot.yml

@@ -2,7 +2,7 @@
 version: 2
 updates:
 - package-ecosystem: pip
-  directory: /dependencies/default
+  directory: /
   schedule:
     interval: weekly
   open-pull-requests-limit: 10

dependencies/default/constraints.txt renamed to constraints.txt

@@ -6,13 +6,13 @@ passenv =
     CI
 
 [pkgenv]
-constraints = dependencies/default/constraints.txt
+constraints = constraints.txt
 
 [testenv]
 package = wheel
 wheel_build_env = .pkg
 extras = testing
-constraints = dependencies/default/constraints.txt
+constraints = constraints.txt
 commands = make test
 allowlist_externals =
     make