Typo fixes

[mzhao80]

Chapter 8: Equivalent Models of Computation

1. Extra period when rendered: ### {.theorem title="Enhanced λ calculus equivalent to pure λ calculus." #enhancedvanillalambdathm} -> ### {.theorem title="Enhanced λ calculus equivalent to pure λ calculus" #enhancedvanillalambdathm}

Chapter 9: Uncomputability:

1. Syntax: Set input of M' as z instead of w in pseudocode for consistency with the text.

Chapter 19: Cryptography

1. Update for consistency with rest of book "$E_k(a NAND b)$" -> "$E_k(NAND(a,b))$
2. Fix typo: "The question of existence of such a scheme" -> The question of the existence of such a scheme"
3. Update for John Nash section "However, he has struggled" -> "However, he struggled"

Chapter 22: Quantum Computing

1. Fix typo "On input a an integer" -> "On input an integer"
2. Fix typo "NAND gates,and so" -> "NAND gates, and so"
3. Fix typo "cummbersome" -> "cumbersome"