Rename the skips in WebIDL to webidl

WebIDL is renamed to webidl at up stream. Rename the skips so we won't
import the files we should skip.

Bug: 1247327
Change-Id: I227fbf60e8529888f13a4b49beaa2702e8110a07
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3154397
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Commit-Queue: Weizhong Xia <weizhong@google.com>
Cr-Commit-Position: refs/heads/main@{#920274}