chore: replace deprecated String.prototype.substr()

.substr() is deprecated so we replace it with .slice() which works similarily but isn't deprecated
Signed-off-by: Tobias Speicher <rootcommander@gmail.com>

.github/actions-scripts/projects.js

@@ -190,7 +190,7 @@ export function generateUpdateProjectNextItemFieldMutation({
     // Strip all non-alphanumeric out of the item ID when creating the mutation ID to avoid a GraphQL parsing error
     // (statistically, this should still give us a unique mutation ID)
     return `
-      set_${fieldID.substr(1)}_item_${item.replaceAll(
+      set_${fieldID.slice(1)}_item_${item.replaceAll(
       /[^a-z0-9]/g,
       ''
     )}: updateProjectNextItemField(input: {