fix: environment stop

[Autoparallel]

Give an overview of the tasks completed
This PR provides a quick fix to the Manager::stop_environment() method by replacing tx_receiver.recv() with tx_receiver.try_recv().

Link to issue(s) that this PR closes
Closes #456

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Please merge after #458

[codecov]

Codecov Report

Merging #459 (81bfd85) into main (880525e) will not change coverage.
Report is 1 commits behind head on main.
The diff coverage is 100.00%.

❗ Current head 81bfd85 differs from pull request most recent head c9300e5. Consider uploading reports for the commit c9300e5 to get more accurate results

@@           Coverage Diff           @@
##             main     #459   +/-   ##
=======================================
  Coverage   58.00%   58.00%           
=======================================
  Files          10       10           
  Lines        3022     3022           
=======================================
  Hits         1753     1753           
  Misses       1269     1269           

Files Changed	Coverage Δ
arbiter-core/src/manager.rs	62.09% <ø> (ø)
arbiter-core/src/middleware.rs	84.52% <ø> (ø)
arbiter-core/src/environment.rs	77.61% <100.00%> (ø)

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[0xJepsen]

this looks good! When we get CI to pass i'll merge in!