relax msprime pinning (#1358)

Author: molpopgen

pyproject.toml

@@ -50,28 +50,31 @@ lint = [
     "flake8",
     "flake8-bugbear",
 ]
+msprime = [
+    "msprime"
+]
 dev = [
 #below are for building package
 #and running tests
     "pytest",
     "pytest-xdist",
     "hypothesis==6.56.4",
-    "msprime ~= 1.3.0",
     "build",
     "twine",
+    {include-group = "msprime"}
 ]
 
 doc = [
     "jupyter-book>=1",
     "pydata-sphinx-theme",
     "matplotlib",
-    "msprime",
     "pandas",
 # pyarrow will be a requirement of pandas soon.
 # right now, not having it raises a warning
     "pyarrow",
     "sphinx-issues",
     "demesdraw~=0.4.0",
+    {include-group = "msprime"},
 ]
 
 [project.scripts]