CI: use php in coverage target

Relates to contributte/contributte#73.

Author: ohmyfelix

Makefile

@@ -46,7 +46,7 @@ tests:
 
 .PHONY: coverage
 coverage:
-	vendor/bin/tester -s -p phpdbg --colors 1 -C --coverage ./coverage.xml --coverage-src ./app tests
+	vendor/bin/tester -s -p php --colors 1 -C --coverage ./coverage.xml --coverage-src ./app tests
 
 .PHONY: dev
 dev: