fix: fix codesmells in retry-handler (#3475)

Author: Uzlopak

lib/handler/retry-handler.js

@@ -281,7 +281,11 @@ class RetryHandler {
       // Weak etags are not useful for comparison nor cache
       // for instance not safe to assume if the response is byte-per-byte
       // equal
-      if (this.etag != null && this.etag.startsWith('W/')) {
+      if (
+        this.etag != null &&
+        this.etag[0] === 'W' &&
+        this.etag[1] === '/'
+      ) {
         this.etag = null
       }
 
@@ -339,6 +343,11 @@ class RetryHandler {
       onRetry.bind(this)
     )
 
+    /**
+     * @this {RetryHandler}
+     * @param {Error} [err]
+     * @returns
+     */
     function onRetry (err) {
       if (err != null || this.aborted || isDisturbed(this.opts.body)) {
         return this.handler.onError(err)