Bug 1554057 [wpt PR 16989] - Update interfaces/wake-lock.idl, a=testonly

Automatic update from web-platform-tests
Update interfaces/wake-lock.idl (#16989)

Source: https://github.com/tidoust/reffy-reports/blob/0ff6a6d/whatwg/idl/wake-lock.idl
Build: https://travis-ci.org/tidoust/reffy-reports/builds/536627667
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wp5At-commits: 96463d14e8693aa16a4376b299ce34a443443cac
wpt-pr: 16989

UltraBlame original commit: d3a38a4c9b1a64c03ef87f77a77600539f73e3ee

Author: marco-c

testing/web-platform/tests/interfaces/wake-lock.idl

@@ -16,5 +16,5 @@ interface WakeLock {
 };
 
 dictionary WakeLockRequestOptions {
-  AbortSignal? signal = null;
+  AbortSignal signal;
 };