Fix building package from source

`pip3 install gimme-aws-creds --no-binary :all: --break-system-packages --verbose` failed because the pyproject.toml file referenced itself.  This made it impossible to deploy via homebrew

pyproject.toml

@@ -1,3 +1,3 @@
 [build-system]
-requires = ["setuptools", "setuptools-rust", "gimme_aws_creds"]
+requires = ["setuptools", "setuptools-rust"]
 build-backend = "setuptools.build_meta"