Fix about compile time flag -Dno_restrictions_augmenter

[zw963]

Need following two fix:

1. Add compile time flag , check https://forum.crystal-lang.org/t/inconsistent-document-about-autocasting/6295/8?u=zw963

2. Fix the example in the Number autocasting, check https://forum.crystal-lang.org/t/inconsistent-document-about-autocasting/6295?u=zw963 too.

[straight-shoota]

#735 fixes 1. already.