build: remove Makefile

Unnecessary as most commands in it are automated now

Makefile

-.PHONY: test
-test:
-# Collect coverage data, but don't report it - for CI build
-	poetry run pytest --cov=pycgtool --cov-report=
-
-.PHONY: cov
-cov:
-	poetry run pytest --cov=pycgtool --cov-fail-under=80
-
-.PHONY: lint
-lint:
-# Lint using only pyflakes - checks for actual errors
-	poetry run prospector --strictness veryhigh --test-warnings --tool pyflakes
-# Lint using range of tools, but don't fail the build if we get warnings
-	poetry run prospector --strictness veryhigh --test-warnings --member-warnings --max-line-length 120 --zero-exit
-
-.PHONY: docs
-docs:
-	SPHINXBUILD="poetry run sphinx-build" make -C docs html
-
-.PHONY: build
-build:
-	poetry build
-
-.PHONY: publish
-publish:
-	rm -rf dist/
-	poetry version prerelease
-	poetry build
-	poetry publish -r testpypi
-
-.PHONY: clean
-clean:
-	rm -f .coverage *.itp* *.gro* *.dat* *.json* *.xtc*
-	rm -rf *.ff