Update copy method deprecation warning to v5

[lachieh]

First steps for #201. Does not close the issue, it just clarifies the warning. Further changes will need to be made to remove the root cause of the warning.

[codecov-io]

Codecov Report

Merging #219 into master will increase coverage by 0.03%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #219      +/-   ##
==========================================
+ Coverage   81.34%   81.38%   +0.03%     
==========================================
  Files          26       26              
  Lines         563      564       +1     
  Branches      103       92      -11     
==========================================
+ Hits          458      459       +1     
+ Misses         84       81       -3     
- Partials       21       24       +3

Impacted Files	Coverage Δ
packages/ssh-pool/src/Connection.js	97.43% <100%> (ø)	⬆️
packages/ssh-pool/src/util.js	95.83% <100%> (+0.18%)	⬆️
packages/ssh-pool/src/commands/tar.js	65.21% <0%> (ø)	⬆️
packages/ssh-pool/src/commands/raw.js	68.75% <0%> (ø)	⬆️

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[gregberge]

Thanks!