Remove some #[allow(warnings)] (#376)

These were probably added during development and then forgotten to be
removed.

src/extract/form.rs

@@ -53,7 +53,6 @@ where
 {
     type Rejection = FormRejection;
 
-    #[allow(warnings)]
     async fn from_request(req: &mut RequestParts<B>) -> Result<Self, Self::Rejection> {
         if req.method() == Method::GET {
             let query = req.uri().query().unwrap_or_default();
@@ -61,8 +60,8 @@ where
                 .map_err(FailedToDeserializeQueryString::new::<T, _>)?;
             Ok(Form(value))
         } else {
-            if !has_content_type(&req, "application/x-www-form-urlencoded")? {
-                Err(InvalidFormContentType)?;
+            if !has_content_type(req, "application/x-www-form-urlencoded")? {
+                return Err(InvalidFormContentType.into());
             }
 
             let body = take_body(req)?;

src/extract/path/mod.rs

@@ -150,7 +150,6 @@ where
 {
     type Rejection = PathParamsRejection;
 
-    #[allow(warnings)]
     async fn from_request(req: &mut RequestParts<B>) -> Result<Self, Self::Rejection> {
         let params = match req
             .extensions_mut()

src/routing/future.rs

@@ -120,7 +120,6 @@ where
 {
     type Output = Result<Response<BoxBody>, S::Error>;
 
-    #[allow(warnings)]
     fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
         loop {
             let mut this = self.as_mut().project();

src/routing/or.rs

@@ -31,7 +31,6 @@ fn traits() {
     assert_sync::<Or<(), ()>>();
 }
 
-#[allow(warnings)]
 impl<A, B, ReqBody> Service<Request<ReqBody>> for Or<A, B>
 where
     A: Service<Request<ReqBody>, Response = Response<BoxBody>> + Clone,
@@ -46,11 +45,11 @@ where
     type Error = A::Error;
     type Future = ResponseFuture<A, B, ReqBody>;
 
-    fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
+    fn poll_ready(&mut self, _cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
         Poll::Ready(Ok(()))
     }
 
-    fn call(&mut self, mut req: Request<ReqBody>) -> Self::Future {
+    fn call(&mut self, req: Request<ReqBody>) -> Self::Future {
         let original_uri = req.uri().clone();
 
         ResponseFuture {

src/service/future.rs

@@ -81,7 +81,6 @@ where
 {
     type Output = Result<Response<BoxBody>, S::Error>;
 
-    #[allow(warnings)]
     fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
         let this = self.project();