Fix type signature for length parameter field in ModService.banLengthToSeconds()

[Sara]

mod-bot/src/api/mod.ts

Lines 48 to 49 in 3c3f469

 static banLengthToSeconds(length: "1h" | "6h" | "12h" | "24h" | "3d" | "7d" | "none" | string): number | undefined { 
 	const seconds = { 

Currently the type of the field is a string, we should cast it to a type "1h" | "6h" | "12h" | "24h" | "3d" | "7d" | "none" in order to better represent the data type