What is the meaning of ripple voltage? and How to calculate a rectifier capacitor?
Figure 30 in your LM7805 datasheet shows an input voltage rejection ratio of about 75 dB around 50 or 60 Hz. That means that you "should" only need to maintain an input ripple below 50 V to keep output ripple below 10 mV. Meaning you should have little issue achieving 10 mV ripple.

Realistically you should probably choose some target input ripple for your regulator (maybe 100 mV), and then choose your rectifier capacitor using that target and the formula in your question.