remove setuptools-sm for art-tools merger

When we do pip install for elliott in merged art-tools repo, setuptools requires it to be a git repo (submodule), which elliott will no longer be.

pyproject.toml

@@ -1,16 +1,12 @@
 [build-system]
 requires = [
     "setuptools>=65.5.1",  # not directly required, pinned by Snyk to avoid a vulnerability
-    "setuptools_scm[toml]>=6.2",
 ]
 build-backend = "setuptools.build_meta"
 
 [tool.setuptools]
 packages = ["elliottlib"]
 
-[tool.setuptools_scm]
-write_to = "elliottlib/_version.py"
-
 [project]
 dynamic = ["version"]
 name="rh-elliott"