You shouldn't have any issues by upgrading these packages, but:
Rolling back to the original packages, in case of problems or broken dependencies, is very easy if you follow these steps.
1 Install Synaptic (package manager) if required
2 Find the first package you wish to downgrade and select it.
3 In the Synaptic toolbar under "Package" select "Force version", then select the desired version you want to downgrade to.
4 Click the button "Force version"
5 Repeat the process for the second package.
6 Press the "apply button" in the Synaptic toolbar to execute the downgrade.
Note: downgrade both packages simultaneously, as I am describing, otherwise you might have fo fix broken dependencies.
Best regards, and have fun with trying out these solutions.
Cool that you figured this out, I hope the developers are reading this thread so they can fix it.
However I don't think users shoul forcefully mess up their libraries and cause dependency issues down the line.
I think the developers at Spotify shouldn't develop on OS's that are not current, neither out-of-date nor nightlies with newer libs. My system is a normal up-to-date Ubuntu 19.04, I have libgnutls30 3.6.5-2 and libcurl3-gnutls 7.64.0-2. There are no upgrades available at this time. I would hope Spotify has some kind of CI pipeline that tests basic features like starting up at allon current systems, but this issue doesn't really seem to indicate they do, or perhaps they didn't make one for 19.04 yet?