Move tomlkit dependency to dev group (#5990)

tomlkit is used only in the packaging tests which are not ordinarily run as
part of the normal workflow of a user or downstream packager.

Signed-off-by: Yaakov Selkowitz <yselkowi@redhat.com>

pyproject.toml

diff --git a/pyproject.toml b/pyproject.toml
index 7a12eed..6a30098 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -57,9 +57,11 @@
 test = [
   "pytest",
   "build",
-  "tomlkit",
 ]
-dev = [{ include-group = "test" }]
+dev = [
+  "tomlkit",
+  { include-group = "test" }
+]
 
 
 [tool.scikit-build]