fix PDF paths in backend readme

Author: alexnuttall

lambdas/backend-api/README.md

@@ -87,7 +87,7 @@ curl -X POST --location "${APIG_STAGE}/v1/template" \
 Will create a single letter template. The CSV form part is optional. Do not set a content type header as this must be auto-generated by curl, so that it includes a form-data boundary.
 
 ```bash
-PDF_PATH="./tests/test-team/fixtures/pdf-upload/no-custom-personalisation/template.pdf"
+PDF_PATH="./tests/test-team/fixtures/pdf-upload/with-personalisation/template.pdf"
 CSV_PATH="./tests/test-team/fixtures/pdf-upload/with-personalisation/test-data.csv"
 ```