Remove obsolete Makefile targets.

The `test` and `coverage` targets rely on `setup.py` which was removed "about
10 years ago". There is apparently no interest in fixing them. This change
removes them to avoid confusion.

As per benoitc#3386

Author: adk-swisstopo

Makefile

@@ -3,12 +3,6 @@ build:
 	venv/bin/pip install -e .
 	venv/bin/pip install -r requirements_dev.txt
 
-test:
-	venv/bin/python setup.py test
-
-coverage:
-	venv/bin/python setup.py test --cov
-
 docs:
 	mkdocs build
 
@@ -20,4 +14,4 @@ clean:
 	@find . -type f -name "*.py[co]" -delete
 	@find . -type d -name "__pycache__" -delete
 
-.PHONY: build clean coverage docs docs-serve test
+.PHONY: build clean docs docs-serve