Disable SoapyOsmo miri by default in favor of SoapyMiri

[nmaster2042]

There is a native SoapySDR Driver SoapyMiri that is working fine: https://github.com/ericek111/SoapyMiri

So mirisdr support can be disabled now to avoid confusion.

[ericek111]

In fact, all that needs to be done is run the https://github.com/pothosware/SoapyOsmo/blob/master/update_gr_osmosdr.sh script. miri support was dropped in upstream.

[guruofquality]

I will do it #13 bit...

Actually I think this particular project probably just needs to go, the community has done a real good job of making soapy support modules. There isnt much left in this little abomination :-)