tests/dns/skr_test modifies testdata/skr/test.skr

Runing skr_test modifies testdata/skr/test.skr. The test passes but leaves artefacts behind which breaks git rebase --exec make unit.

-;; SignedKeyResponse 1.0 20240813095451 (Tue Aug 13 11:54:51 2024)
+;; SignedKeyResponse 1.0 20240904034825 (Wed Sep  4 13:48:25 2024)
 test.                  3600    IN      DNSKEY  257 3 13 evPZ03dt9VeWNQKqw1fpuL0V1RcyPRge4s306hGOVYg1a1IttOf3ZKIm McMgdT1K4nxJ+S7BtX6RVECqzp1rAA==
 test.                  3600    IN      DNSKEY  256 3 13 GIyBcxr9uBJvybXw2eOeZ1nWjRd+0INxUPlKaWI1KQxJwWRJTOJMw33g SSCz++TBmKyXm5ghl+56vOkoO33ppg==
-test.                  3600    IN      RRSIG   DNSKEY 13 1 3600 20240823095451 20240813085451 43204 test. v7TY2u81mFfOsL3b3kGk1vV+dUdOBbBb2YrIAvAJ6v9T7/wS2U4X8125 QuYPNo2OpQEvcNI//LZFjtFDiz1foQ==
+test.                  3600    IN      RRSIG   DNSKEY 13 1 3600 20240914034825 20240904024825 43204 test. mxsCEIasawi1z+oK6sQ99vHTh0dSlvHkeiyaq2k1EPUL+1cvjJ0MEBb0 mAtOZ0t9MtXGB54Vf7oP3sQ18FXcog==
 test.                  3600    IN      CDNSKEY 257 3 13 evPZ03dt9VeWNQKqw1fpuL0V1RcyPRge4s306hGOVYg1a1IttOf3ZKIm McMgdT1K4nxJ+S7BtX6RVECqzp1rAA==
-test.                  3600    IN      RRSIG   CDNSKEY 13 1 3600 20240823095451 20240813085451 43204 test. zA/Ia+miTFmdriALov2J3SZftWJnpiTinyxuQr/2spkLt3aBG1ZgEr7V 25/8hW4vEYYBdP6CTbNClMWlh1FTGA==
+test.                  3600    IN      RRSIG   CDNSKEY 13 1 3600 20240914034825 20240904024825 43204 test. p5p7PuKseMitA6gy3qxlTqdCyMoJidPHGlQz1nq1KmF327PWLZJcLzIu /o8PPR7cCIVkGybkxuSsBJ2HeU/B8g==
...