tools: don't lint-md as part of main lint target

PR-URL: #17587
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Myles Borins <myles.borins@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

Makefile

@@ -1120,7 +1120,6 @@ lint: ## Run JS, C++, MD and doc linters.
 	@EXIT_STATUS=0 ; \
 	$(MAKE) lint-js || EXIT_STATUS=$$? ; \
 	$(MAKE) lint-cpp || EXIT_STATUS=$$? ; \
-	$(MAKE) lint-md || EXIT_STATUS=$$? ; \
 	$(MAKE) lint-addon-docs || EXIT_STATUS=$$? ; \
 	exit $$EXIT_STATUS
 CONFLICT_RE=^>>>>>>> [0-9A-Fa-f]+|^<<<<<<< [A-Za-z]+