Update: PublisherERS.ts to include rc as a channel

[craigwduckett]

• [x] I have read the contribution documentation for this project.
• [x] I agree to follow the code of conduct that this project follows, as appropriate.
• [x] The changes are appropriately documented (if applicable).
• [x] The changes have sufficient test coverage (if applicable).
• [x] The testsuite passes successfully on my local machine (if applicable).

Summarize your changes: Added a check to ERS uploader for rc channel in the version string as this is one of the default channels created in ERS.

[codecov[bot]]

Codecov Report

Merging #1219 into master will increase coverage by 0.3%. The diff coverage is n/a.

@@            Coverage Diff            @@
##           master    #1219     +/-   ##
=========================================
+ Coverage   67.82%   68.13%   +0.3%     
=========================================
  Files          67       67             
  Lines        1958     1958             
  Branches      378      378             
=========================================
+ Hits         1328     1334      +6     
+ Misses        454      451      -3     
+ Partials      176      173      -3

Impacted Files	Coverage Δ
packages/api/cli/src/util/check-system.ts	78.94% <0%> (+5.26%)	:arrow_up:
packages/api/core/src/util/electron-version.ts	96.07% <0%> (+7.84%)	:arrow_up:

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