check-commit: update test expectation per removal of "double empty line" rule

Follow up for 47084b5ffd80.

tests/test-contrib-check-commit.t

@@ -130,10 +130,6 A patch with other errors:
    This has no topic and ends with a period.
   7: don't add trailing period on summary line
    This has no topic and ends with a period.
-  19: adds double empty line
-   +
   20: adds a function with foo_bar naming
    + def blah_blah(x):
-  23: adds double empty line
-   +
   [1]