[kaltura] Ignore Widevine encrypted video (.wvm)

There is currently no public method to decrypt this, and there may be
other streams available that can be downloaded.

Example URL, has `.wvm` and `.mp4` formats:
https://www.voot.com/shows/bigg-boss-s11/11/538936/bigg-boss-extra-dose-arshi-s-quirky-demand/541700

youtube_dl/extractor/kaltura.py

@@ -287,6 +287,9 @@ class KalturaIE(InfoExtractor):
             # skip for now.
             if f.get('fileExt') == 'chun':
                 continue
+            # DRM-protected video, cannot be decrypted
+            if f.get('fileExt') == 'wvm':
+                continue
             if not f.get('fileExt'):
                 # QT indicates QuickTime; some videos have broken fileExt
                 if f.get('containerFormat') == 'qt':