Fix new warnings on Nightly

src/emitter.rs

@@ -1,7 +1,5 @@
 use std::collections::VecDeque;
 
-use alloc::string::String;
-
 use crate::macros::{
     is_alpha, is_ascii, is_blank, is_blankz, is_bom, is_break, is_breakz, is_printable, is_space,
 };

src/lib.rs

@@ -167,8 +167,6 @@ pub enum MappingStyle {
 
 #[cfg(test)]
 mod tests {
-    use alloc::vec::Vec;
-
     use super::*;
 
     #[test]

src/macros.rs

@@ -215,3 +215,18 @@ macro_rules! IS_BLANKZ {
         IS_BLANKZ_AT!($string, 0)
     };
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn printable() {
+        for ch in "🎉".chars() {
+            assert!(is_printable(ch));
+        }
+        for ch in "\u{1f389}".chars() {
+            assert!(is_printable(ch));
+        }
+    }
+}

src/parser.rs

@@ -1,6 +1,3 @@
-use alloc::string::String;
-use alloc::{vec, vec::Vec};
-
 use crate::scanner::Scanner;
 use crate::{
     Encoding, Error, Event, EventData, MappingStyle, Mark, Result, ScalarStyle, SequenceStyle,

src/scanner.rs

@@ -1,7 +1,5 @@
 use std::collections::VecDeque;
 
-use alloc::string::String;
-
 use crate::macros::{is_blankz, is_break};
 use crate::reader::yaml_parser_update_buffer;
 use crate::{