[workflow] Fixing double run when creating a PR

[gagoar]

Currently, the workflow runs twice every PR. This is caused by push and on pull_request events.
Sadly the documentation says that it will be an or.

But in practice, this triggers twice.

Alternatively, we could just leave push

on:  push

this is visible when inspecting some of the PR's

every step produces 2 runs (one for push the other for pull_request)
example for pull request
example for push

this is also visible in #2757

[gagoar]

I have a check failing that I can't reproduce. also I'm not changing code.

> graphql@15.4.0 prettier:check /base/graphql-js
> prettier --check .

Checking formatting...
All matched files use Prettier code style!

[IvanGoncharov]

I have a check failing that I can't reproduce. also I'm not changing code.

@gagoar In logs you will see:

[gagoar]

I have a check failing that I can't reproduce. also I'm not changing code.

@gagoar In logs you will see:

I've run this on my computer but I can't seem to see what's the wrong part with what I've changed. can you tell me what is wrong?

also what I've changes can't be written differently

[yaacovCR]

This can probably be closed considering all the improvements by @IvanGoncharov within our use of GitHub actions. Feel free to reopen as necessary.