gstreamer/sample: Silence clippy warning

warning: methods called `new` usually return `Self`
   --> gstreamer/src/sample.rs:107:5
    |
107 | /     pub fn new<'a>() -> SampleBuilder<'a> {
    | |_____^

gstreamer/src/sample.rs

@@ -104,6 +104,7 @@ impl<'a> SampleBuilder<'a> {
 }
 
 impl Sample {
+    #[allow(clippy::new_ret_no_self)]
     pub fn new<'a>() -> SampleBuilder<'a> {
         SampleBuilder {
             buffer: None,