Update bitsandbytes, relax its version constraint

[mryab]

It was reported that the current version of bitsandbytes used in hivemind[bitsandbytes] has an error that prevents it from working properly. The first tested release that we can rely on is 0.34.0, which is what I use in this PR. Also, to provide a bit more compatibility with future patches of this release, I've changed the dependency specification from strict equality to compatibility with future patches of 0.34.

Notably, if a user wants to use newer versions of bitsandbytes in their applications, they can simply install hivemind (without [bitsandbytes]) and bitsandbytes separately: this way, there will be no version conflicts.

[codecov]

Codecov Report

Merging #510 (7f88a9e) into master (13cdd13) will decrease coverage by 0.03%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #510      +/-   ##
==========================================
- Coverage   75.97%   75.94%   -0.04%     
==========================================
  Files          81       81              
  Lines        7943     7943              
==========================================
- Hits         6035     6032       -3     
- Misses       1908     1911       +3     

Impacted Files	Coverage Δ
hivemind/dht/node.py	90.28% <0.00%> (-1.66%)	⬇️
hivemind/dht/protocol.py	93.15% <0.00%> (+0.45%)	⬆️
hivemind/moe/server/server.py	44.26% <0.00%> (+0.54%)	⬆️
hivemind/moe/server/runtime.py	70.00% <0.00%> (+0.83%)	⬆️
hivemind/moe/server/connection_handler.py	47.91% <0.00%> (+1.04%)	⬆️