graphicsmagick version update failing

From the status page:

```
The recipe did not change in the version migration, a URL did not hash, or there is jinja2 syntax the bot cannot handle!

Please check the URLs in your recipe with version '1.3.36' to make sure they exist!

We also found the following errors:

- no URLs in the source section
```

Guessing it is getting hung up on this line, which should be ignored

https://github.com/conda-forge/graphicsmagick-feedstock/blob/08048c5face0aa6c248623d715f1813e2cdc6696/recipe/meta.yaml#L12