Continue update even if csp patch is missing

This can happen if you run the update multiple times and it was already
deleted from another run but not regenerated yet due to an early
failure like from a conflict.

ci/build/update-vscode.sh

@@ -79,7 +79,7 @@ function get-webview-script-hash() {
 }
 
 function delete_csp() {
-  quilt delete csp-hashes.diff
+  quilt delete csp-hashes.diff || true
 }
 
 function update_csp() {