Remove unused start_worker argument to default_worker

[omus]

Minor cleanup. Depends on PR: beacon-biosignals/ray#9.

Note that if beacon-biosignals/ray#9 is merged prior to this PR being merged then start_worker() will break as we currently require this unused argument.

[omus]

Turns out that if the backend still passes in the argument then our tests here will hang as the workers never come up due to:

too many arguments
usage: <PROGRAM> [--ray_raylet_socket_name RAYLET_SOCKET]
                 [--ray_plasma_store_socket_name STORE_SOCKET]
                 [--ray_address ADDRESS]
                 [--ray_node_manager_port NODE_MANAGER_PORT]
                 --ray_node_ip_address NODE_IP_ADDRESS
                 [--ray_redis_password REDIS_PASSWORD]
                 [--ray_session_dir SESSION_DIR]
                 [--ray_logs_dir LOGS_DIR]
                 [--runtime-env-hash RUNTIME_ENV_HASH]
                 [--startup_token STARTUP_TOKEN]

I'll make an additional PR to make this argument optional so we can have a nice clean merge order

[codecov]

Codecov Report

Merging #117 (75cf134) into main (b967b8a) will increase coverage by 0.18%.
Report is 1 commits behind head on main.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #117      +/-   ##
==========================================
+ Coverage   74.44%   74.63%   +0.18%     
==========================================
  Files           8        8              
  Lines         407      406       -1     
==========================================
  Hits          303      303              
+ Misses        104      103       -1     

Flag	Coverage Δ
Ray.jl	74.63% <ø> (+0.18%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
src/runtime.jl	54.01% <ø> (+0.28%)	⬆️

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