📖 Fix Comment in wad_exp (#212)

### 🕓 Changelog

Revise the comment in `wad_exp` from `< 0.5` to `< 1` to ensure consistency with the implementation.

Signed-off-by: gbaleeee <53768199+zhouxianyuan@users.noreply.github.com>

src/snekmate/utils/Math.vy

@@ -431,7 +431,7 @@ def wad_exp(x: int256) -> int256:
     """
     value: int256 = x
 
-    # If the result is `< 0.5`, we return zero. This happens when we have the following:
+    # If the result is `< 1`, we return zero. This happens when we have the following:
     # "x <= (log(1e-18) * 1e18) ~ -4.15e19".
     if (x <= -41_446_531_673_892_822_313):
         return empty(int256)