chore: make script compatible with actions/github-script@v6.0.0

.github/workflows/testing.yml

diff --git a/.github/workflows/testing.yml b/.github/workflows/testing.yml
index 281f9bb..21936c7 100644
--- a/.github/workflows/testing.yml
+++ b/.github/workflows/testing.yml
@@ -93,7 +93,7 @@
               const branch = 'update-discovery-artifacts-${{ steps.date.outputs.current_date }}'
               let prBody = `${{ steps.pr_body.outputs.change_summary }}`
               const prTitle = 'chore: Update discovery artifacts'
-              const pullRequests = await github.pulls.list({
+              const pullRequests = await github.rest.pulls.list({
                 owner: owner,
                 repo: repo,
                 head: `${owner}:${branch}`,
@@ -102,7 +102,7 @@
 
               if (pullRequests.data.length === 1) {
                 prNumber = pullRequests.data[0].number
-                await github.pulls.update({
+                await github.rest.pulls.update({
                   owner: owner,
                   repo: repo,
                   pull_number: prNumber,
@@ -111,7 +111,7 @@
                 })
                 console.log('Updated PR')
               } else {
-                const createPrResult = await github.pulls.create({
+                const createPrResult = await github.rest.pulls.create({
                   owner: owner,
                   repo: repo,
                   base: 'main',