chore: fix clippy warnings

src/core/pool.rs

@@ -36,7 +36,7 @@ impl Pool {
     pub fn create_buffer_from_str(&mut self, str: &str) -> Option<TemporaryBuffer> {
         let mut buffer = self.create_buffer(str.len())?;
         unsafe {
-            let mut buf = buffer.as_ngx_buf_mut();
+            let buf = buffer.as_ngx_buf_mut();
             ptr::copy_nonoverlapping(str.as_ptr(), (*buf).pos, str.len());
             (*buf).last = (*buf).pos.add(str.len());
         }

src/http/request.rs

@@ -311,7 +311,7 @@ impl Request {
         };
 
         // previously call of ngx_http_subrequest() would ensure that the pointer is not null anymore
-        let mut sr = unsafe { &mut *psr };
+        let sr = unsafe { &mut *psr };
 
         /*
          * allocate fake request body to avoid attempts to read it and to make

src/log.rs

@@ -199,9 +199,9 @@ mod tests {
         let mock = MockLog { log_level: 16 };
 
         let mut r = check_mask(DebugMask::Core, mock.log_level);
-        assert!(r == true);
+        assert!(r);
 
         r = check_mask(DebugMask::Alloc, mock.log_level);
-        assert!(r == false);
+        assert!(!r);
     }
 }