Remove unnecessary lines

- originally proposed by `0xpessimist` in stacks-network#5879 via stacks-network/docs#1710

Author: wileyj

clarity/src/vm/docs/mod.rs

@@ -499,7 +499,6 @@ Note: Corner cases are handled with the following rules:
   * if both `i1` and `i2` are `0`, return `1`
   * if `i1` is `1`, return `1`
   * if `i1` is `0`, return `0`
-  * if `i2` is `1`, return `i1`
   * if `i2` is negative or greater than `u32::MAX`, throw a runtime error",
     example: "(pow 2 3) ;; Returns 8
 (pow 2 2) ;; Returns 4