Fix clippy: Do not manually check for None

Signed-off-by: Matthias Beyer <[email protected]>

Author: matthiasbeyer

src/env.rs

@@ -140,7 +140,7 @@ impl Environment {
     /// Once list_separator is set, the type for string is [`Vec<String>`].
     /// To switch the default type back to type Strings you need to provide the keys which should be [`Vec<String>`] using this function.
     pub fn with_list_parse_key(mut self, key: &str) -> Self {
-        if self.list_parse_keys == None {
+        if self.list_parse_keys.is_none() {
             self.list_parse_keys = Some(vec![key.into()])
         } else {
             self.list_parse_keys = self.list_parse_keys.map(|mut keys| {