espanso: fix test for nixpkgs update

Recent nixpkgs update made a small change how YAML is generated,
causing the test YAML to be out of date.

The replacement match is also an exact example from the espanso wiki
https://espanso.org/docs/matches/basics/#multi-line-expansions.

tests/modules/services/espanso/basic-matches.yaml

@@ -10,9 +10,7 @@ global_vars:
 matches:
 - replace: It's {{currentdate}} {{currenttime}}
   trigger: :now
-- replace: 'line1
-
-    line2'
+- replace: "line1\nline2"
   trigger: :hello
 - regex: :hi(?P<person>.*)\.
   replace: Hi {{person}}!