util/testing/Makefile.inc: Add new line as help section separator

coreboot test targets help section was missing an empty line at the end.
This caused the next help section to be visually merged with it.
Empty line makes help output more aesthetic.

Signed-off-by: Jakub Czapiga <jacz@semihalf.com>
Change-Id: I2f7202b0a636f62b60788215058611c9c86183de
Reviewed-on: https://review.coreboot.org/c/coreboot/+/54367
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Paul Fagerburg <pfagerburg@chromium.org>

util/testing/Makefile.inc

@@ -10,6 +10,7 @@ test-help help::
 	@echo  '  test-abuild            - basic: Builds all platforms'
 	@echo  '  test-payloads          - basic: Builds internal payloads'
 	@echo  '  test-cleanup           - basic: Cleans coreboot directories'
+	@echo
 
 # junit.xml is a helper target to wrap builds that don't create junit.xml output
 # BLD = The name of the build