Fix invalid syntax expression in Comparisons concept introduction.md

Programming C++
1

Hello,

There is an invalid syntax expression in Introduction.md for Comparisons concept:
bool eq3 == 3; // false, integer comparison
I propose changing it to:
bool eq3 = 2 == 3; // false, integer comparison

The change is in this pull request.

Thank you.

2

Thanks for the PR, I reopened it and added a comment.