Fix publish workflow

[Widcket]

• All new/changed/fixed functionality is covered by tests (or N/A)
• I have added documentation for all new/changed functionality (or N/A)

📋 Changes

This PR fixes the CI publish workflow, as it was failing because the dart-lang/setup-dart/.github/workflows/publish.yml@v1 action installs dependencies using dart pub get, but our packages depend on Flutter, and as such need to use flutter pub get instead:

But still the Dart SDK needs to be installed using that action, as it contains the logic necessary for getting the token used for publishing.

Unlike that action, we're not adding a dry run step because it returns a non-zero error code (that fails the workflow) when there are warnings, and the auth0_flutter package produces warnings:

We won't be fixing the warning marked with red; the scenario the warning is about does not apply for auth0_flutter, which will always depend on a specific version of auth0_flutter_platform_interface.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (253209a) 96.08% compared to head (980ed82) 95.80%.
Report is 22 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #339      +/-   ##
============================================
- Coverage     96.08%   95.80%   -0.29%     
============================================
  Files            97       76      -21     
  Lines          1611     1121     -490     
  Branches        331      281      -50     
============================================
- Hits           1548     1074     -474     
+ Misses           49       46       -3     
+ Partials         14        1      -13     

Flag	Coverage Δ
auth0_flutter	100.00% <100.00%> (ø)
auth0_flutter_android	?
auth0_flutter_ios	?
auth0_flutter_platform_interface	87.03% <100.00%> (ø)

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

Files	Coverage Δ
...lib/src/web/extensions/user_profile_extension.dart	100.00% <100.00%> (ø)
...lutter_platform_interface/lib/src/credentials.dart	100.00% <100.00%> (ø)

... and 23 files with indirect coverage changes

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