fix: don't double wrap URIs for HLS key requests (#6246)

The `constructSegmentUris` util already returns an array, so the call to `makeRequest` was being made with an array of arrays. This wasn't causing errors for requests that use the `fetch` plugin, since `fetch` will stringify the first argument if it's an array. But the data URI plugin expects to receive a string and calls `.split()` on it, so keys using data URIs throw an error if the URI is wrapped in an array.

Thanks to #6243 and @andrew0

Backported to v4.7.x

lib/hls/hls_parser.js

@@ -2831,12 +2831,12 @@ shaka.hls.HlsParser = class {
     // Don't download the key object until the segment is parsed, to avoid a
     // startup delay for long manifests with lots of keys.
     keyInfo.fetchKey = async () => {
-      const keyUri = shaka.hls.Utils.constructSegmentUris(
+      const keyUris = shaka.hls.Utils.constructSegmentUris(
           getUris(), drmTag.getRequiredAttrValue('URI'), variables);
 
       const requestType = shaka.net.NetworkingEngine.RequestType.KEY;
       const request = shaka.net.NetworkingEngine.makeRequest(
-          [keyUri], this.config_.retryParameters);
+          keyUris, this.config_.retryParameters);
       const keyResponse = await this.makeNetworkRequest_(request, requestType);
 
       // keyResponse.status is undefined when URI is "data:text/plain;base64,"