Use access token GIX_CREATE_PR_PAT instead of GIX_SNSDEMO_BOT_GH_TOKEN (

#393)

# Motivation

The [latest
run](https://github.com/dfinity/snsdemo/actions/runs/10553072245/job/29232813566)
to update the IC commit in snsdemo, had the following error:
```
fatal: could not read Username for 'https://github.com': No such device or address
```

After some searching, I found
[this](peter-evans/create-pull-request#2094),
indicating that this is an issue with the access token.

After switching from `GIX_SNSDEMO_BOT_GH_TOKEN` to `GIX_CREATE_PR_PAT`,
the issue went away.
We already use `GIX_CREATE_PR_PAT` in `nns-dapp`, `ic-js` and
`gix-components` so it seems fine to use in snsdemo as well. The snsdemo
repo already had access to the token.

# Changes

Change the version of `peter-evans/create-pull-request` that we use from
v4 to v5.

# Tests

Ran the workflow from the branch and it succeeded:

https://github.com/dfinity/snsdemo/actions/runs/10556505138/job/29242171471
And it created this PR:
#392

.github/workflows/update-dfx.yml

@@ -44,7 +44,7 @@ jobs:
         if: ${{ steps.update.outputs.updated == '1' }}
         uses: peter-evans/create-pull-request@v4
         with:
-          token: ${{ secrets.GIX_SNSDEMO_BOT_GH_TOKEN }}
+          token: ${{ secrets.GIX_CREATE_PR_PAT }}
           base: main
           add-paths: |
             dfx.json

.github/workflows/update-ic.yml

@@ -49,7 +49,7 @@ jobs:
         if: ${{ steps.update.outputs.updated == '1' }}
         uses: peter-evans/create-pull-request@v4
         with:
-          token: ${{ secrets.GIX_SNSDEMO_BOT_GH_TOKEN }}
+          token: ${{ secrets.GIX_CREATE_PR_PAT }}
           base: main
           add-paths: |
             bin/versions.bash