internal/website: try using a different syntax for GITHUB_TOKEN

[vangent]

The push started failing, no idea why:
https://travis-ci.com/github/google/go-cloud/jobs/468898520

The current documentation says ${{ secrets.GITHUB_TOKEN }} instead of just $GITHUB_TOKEN, so let's try that and see if it works (https://docs.github.com/en/free-pro-team@latest/actions/reference/authentication-in-a-workflow#using-the-github_token-in-a-workflow).

[codecov]

Codecov Report

Merging #2942 (6f94604) into master (e840397) will increase coverage by 0.17%.
The diff coverage is 77.98%.

@@            Coverage Diff             @@
##           master    #2942      +/-   ##
==========================================
+ Coverage   69.22%   69.39%   +0.17%     
==========================================
  Files         110      111       +1     
  Lines       11447    11547     +100     
==========================================
+ Hits         7924     8013      +89     
- Misses       2876     2878       +2     
- Partials      647      656       +9     

Impacted Files	Coverage Δ
pubsub/azuresb/azuresb.go	21.60% <0.00%> (-0.09%)	⬇️
runtimevar/gcpsecretmanager/gcpsecretmanager.go	79.16% <79.16%> (ø)
blob/azureblob/azureblob.go	76.53% <100.00%> (ø)
docstore/awsdynamodb/urls.go	56.52% <100.00%> (+1.97%)	⬆️
pubsub/awssnssqs/awssnssqs.go	83.22% <100.00%> (+0.05%)	⬆️
pubsub/kafkapubsub/kafka.go	81.81% <100.00%> (ø)
runtimevar/filevar/filevar.go	83.87% <0.00%> (-1.08%)	⬇️
blob/s3blob/s3blob.go	89.47% <0.00%> (+0.52%)	⬆️
internal/retry/retry.go	100.00% <0.00%> (+7.69%)	⬆️
... and 1 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 2ca430d...6f94604. Read the comment docs.