Reflow test to ensure trailing space is preserved

Many editors strip trailing space, so avoid using a multiline
string where the space is actually needed.

test/test_api/test_call_signatures.py

@@ -121,11 +121,8 @@ def test_multiple_signatures(Script):
 
 
 def test_get_signatures_whitespace(Script):
-    s = dedent("""\
+    # note: trailing space after 'abs'
-    abs(
+    s = 'abs( \ndef x():\n    pass\n'
-    def x():
-        pass
-    """)
     assert_signature(Script, s, 'abs', 0, line=1, column=5)