Mark rejected alternative proposals with a red color in PEP

[vainaixr]

current scenario -

1. The rejected alternative proposals are marked with the same color as the code that actually works

2. If one is scrolling up, then one might not be able to tell that a particular point belongs to a rejected alternative proposal,
   
   

expected scenario -

1. Mark rejected alternative proposals with a different heading color (most likely red or black)
2. End the rejected alternative proposals with a line,

This marks the end of rejected alternative proposals

or

--------------- Rejected Alternative Proposals End -----------------