Remove Makefile rule clean-dev

From npm ci docs https://docs.npmjs.com/cli/v7/commands/npm-ci:

If a node_modules is already present, it will be automatically removed
before npm ci begins its install.

Unnecessary since b595d86e96.

Signed-off-by: François Freitag <mail@franek.fr>

Makefile

@@ -1,7 +1,7 @@
 all: clean dev-setup build-js-production
 
 # Dev env management
-dev-setup: clean clean-dev npm-init
+dev-setup: clean npm-init
 
 npm-init:
 	npm ci
@@ -43,9 +43,6 @@ clean:
 	rm -rf apps/workflowengine/js/
 	rm -rf core/js/dist
 
-clean-dev:
-	rm -rf node_modules
-
 clean-git: clean
 	git checkout -- apps/accessibility/js/
 	git checkout -- apps/comments/js/