doc, test: clean up from 'better tracing of pytracer changed'

Commit d35e8c4 changed the message, but the
docs and tests weren't updated.

Author: nedbat

doc/cmd.rst

@@ -236,8 +236,7 @@ could affect the measurement process.  The possible warnings include:
   During reporting, a file was thought to be Python, but it couldn't be parsed
   as Python.
 
-* ``Trace function changed, measurement is likely wrong: XXX (trace-changed)``
-  |br|
+* ``Trace function changed, data is likely wrong: XXX (trace-changed)`` |br|
   Coverage measurement depends on a Python setting called the trace function.
   Other Python code in your product might change that function, which will
   disrupt coverage.py's measurement.  This warning indicates that has happened.

tests/test_oddball.py

@@ -83,7 +83,7 @@ def recur(n):
     def test_long_recursion(self):
         # We can't finish a very deep recursion, but we don't crash.
         with pytest.raises(RuntimeError):
-            with swallow_warnings("Trace function changed, measurement is likely wrong: None"):
+            with swallow_warnings("Trace function changed, data is likely wrong: None"):
                 self.check_coverage("""\
                     def recur(n):
                         if n == 0:
@@ -120,7 +120,7 @@ def recur(n):
             """)
 
         cov = coverage.Coverage()
-        with swallow_warnings("Trace function changed, measurement is likely wrong: None"):
+        with swallow_warnings("Trace function changed, data is likely wrong: None"):
             self.start_import_stop(cov, "recur")
 
         pytrace = (cov._collector.tracer_name() == "PyTracer")