Bandwidth file spec v1.5 adds Tor version but sbws adds Tor version with bandwidth file spec as v1.4

Reported by @atagar in irc #tor-dev:

22:53 <+    atagar> juga, karsten: Our bandwidth file spec says that the most recent version is 1.5.0 to add a tor_version attribute (https://gitweb.torproject.org/torspec.git/commit/?id=7d8b4bc). However, 
                    CollecTor's most recent bandwidth files (https://collector.torproject.org/recent/relay-descriptors/bandwidths/) say that they're version 1.4.0 yet include a tor_version. Maybe our bandwidth 
                    scanners added this
22:53 <+    atagar> attribute without updating their version number?
22:54 <+    atagar> If so since this has been live for a while we should probably simply change the spec to say that tor_version is a 1.4.0 attribute, and that we don't have a version 1.5.0.

probably we forgot to update the bandwidth file spec in the sbws's generated bandwidth file.

I'm not sure whether we should change it in the bandwidth spec or in sbws, since bandwidth spec also says v1.5 adds other things.