Remove make upstream from preTest

[blampe]

After pulumi/ci-mgmt#1151 our make targets should now all correctly call make upstream if they need it.

This PR removes the make upstream step from preTest and updates examples/webserver-go/go.mod to no longer break make ci-mgmt.

[github-actions]

Does the PR have any schema changes?

Looking good! No breaking changes found.
No new resources/functions.

Maintainer note: consult the runbook for dealing with any breaking changes.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 24.41%. Comparing base (df65048) to head (0183dcd).
Report is 2 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #4935   +/-   ##
=======================================
  Coverage   24.41%   24.41%           
=======================================
  Files         360      360           
  Lines      143270   143270           
=======================================
  Hits        34984    34984           
  Misses     108187   108187           
  Partials       99       99           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[pulumi-bot]

This PR has been shipped in release v6.66.0.