Bug 1665521 [wpt PR 25582] - Update interfaces/webxr-hand-input.idl, a=testonly

Automatic update from web-platform-tests
Update interfaces/webxr-hand-input.idl

Note: This file was recently manually updated in commit 15e47f779c.
      This commit may revert some of those changes.

Source: https://github.com/w3c/webref/blob/f1e6afa/ed/idl/webxr-hand-input.idl
Build: https://travis-ci.org/w3c/webref/builds/184809220

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wpt-commits: 6b09ae888799869b8dd5ad9ee9af8cbe14517da5
wpt-pr: 25582

testing/web-platform/tests/interfaces/webxr-hand-input.idl

@@ -54,5 +54,5 @@ partial interface XRFrame {
 };
 
 interface XRJointPose: XRPose {
-    readonly attribute float? radius;
+    readonly attribute float radius;
 };