monotone: replace %s interpolation with appropriate numeric specifiers

The length is an int, and the version is a float.  Neither work with bytes on
py3.  This was noticed when looking at nearby code after updating pytype changed
some signatures.

hgext/convert/monotone.py

@@ -160,7 +160,7 b' class monotone_source(common.converter_s'
             raise error.Abort(
                 _(
                     b"bad mtn packet - unable to read full packet "
-                    b"read %s of %s"
+                    b"read %s of %d"
                 )
                 % (len(read), length)
             )
@@ -398,7 +398,7 b' class monotone_source(common.converter_s'
                     )
         else:
             self.ui.debug(
-                b"mtn automate version %s - not using automate stdio "
+                b"mtn automate version %f - not using automate stdio "
                 b"(automate >= 12.0 - mtn >= 0.46 is needed)\n" % version
             )