tests/bloom_bytes: explicitely expect a float

The last line should be a float lower than 1 so 0.XXX.
So expect it to match this.

This should prevent issues when float printing does not work.

tests/bloom_bytes/tests/01-run.py

@@ -20,7 +20,7 @@ def testfunc(child):
     child.expect(r"checking 10000 elements took \d+ms", timeout=TIMEOUT)
     child.expect(r"\d+ elements probably in the filter.")
     child.expect(r"\d+ elements not in the filter.")
-    child.expect(".+ false positive rate.")
+    child.expect(r"0\.\d+ false positive rate.")
     child.expect_exact("All done!")