Fix pretty printing for Not(Equivalent) and Not(Implies). fixes #7179
Fix latex printing for Not(Equivalent) and Not(Implies).
Make equivalence symbol same for pretty printer and latex printer
and change not equivalent symbol to u+2262 [skip ci]
Wrap unicode chars with u and fix a bug in latex printer
Add tests for printing Equivalent. fixes #7180
Remove double wrapping with u
Remove unnecessary if block
Add tests for pretty printer
Merge pull request #7541 from debugger22/7179

Fixes printing for Not(Equivalent) and Not(Implies).