Fix implicit string concatenation in tests-checkds.py

pylint 2.14.2 reports the following warnings (implicit-str-concat):

bin/tests/system/checkds/tests-checkds.py:265:0: W1404: Implicit string concatenation found in call (implicit-str-concat)
bin/tests/system/checkds/tests-checkds.py:273:0: W1404: Implicit string concatenation found in call (implicit-str-concat)

One might prefer to fix them in line with the rest of wait_for_log() invocations, but black CI job disagrees:

black.patch

diff --git a/bin/tests/system/checkds/tests-checkds.py b/bin/tests/system/checkds/tests-checkds.py
index 4dbce9a..56777fb 100755
--- a/bin/tests/system/checkds/tests-checkds.py
+++ b/bin/tests/system/checkds/tests-checkds.py
@@ -262,8 +262,7 @@ def test_checkds_dspublished(named_port):
     zone_check(server, "dspublished.checkds.")
     wait_for_log(
         "ns9/named.run",
-        "zone dspublished.checkds/IN (signed): checkds: "
-        "DS response from 10.53.0.2",
+        "zone dspublished.checkds/IN (signed): checkds: " "DS response from 10.53.0.2",
     )
     keystate_check(parent, "dspublished.checkds.", "DSPublish")
 
@@ -271,8 +270,7 @@ def test_checkds_dspublished(named_port):
     zone_check(server, "reference.checkds.")
     wait_for_log(
         "ns9/named.run",
-        "zone reference.checkds/IN (signed): checkds: "
-        "DS response from 10.53.0.2",
+        "zone reference.checkds/IN (signed): checkds: " "DS response from 10.53.0.2",
     )
     keystate_check(parent, "reference.checkds.", "DSPublish")