test: Minor refactor to reduce test code duplication

Signed-off-by: Magnus Malm <magnusmalm@gmail.com>

test/test_add_remove_dynamic_service/test.sh

@@ -6,10 +6,6 @@ TEST_DIR=$(dirname "$0")/..
 # shellcheck source=/dev/null
 . "$TEST_DIR/lib.sh"
 
-assert_num_children() {
-    assert "$1 services are running" "$(texec pgrep -P 1 "$2" | wc -l)" -eq "$1"
-}
-
 test_teardown() {
     say "Test done $(date)"
     say "Running test teardown..."