fix: fix workflow branch specification

[wschurman]

Why

The main branch was changed from master to main, but the CI wasn't updated. This is causing codecov and CI not to run on the main branch.

How

Update the workflow.

Test Plan

Wait for CI.

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (main@0dbf5e9). Click here to learn what that means.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #179   +/-   ##
=======================================
  Coverage        ?   96.17%           
=======================================
  Files           ?       80           
  Lines           ?     1985           
  Branches        ?      257           
=======================================
  Hits            ?     1909           
  Misses          ?       71           
  Partials        ?        5           

Flag	Coverage Δ
integration	96.17% <0.00%> (?)
unittest	96.17% <0.00%> (?)

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[ide]

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