move Johan from contributors to acknowledgements (#839)

Author: samuelweiler

index.bs

@@ -40,7 +40,6 @@ Former Editor: Hubert Le Van Gong, w3cid 84817, PayPal, hlevangong@paypal.com
 !Contributors: <a href="mailto:agl@google.com">Adam Langley</a> (Google)
 !Contributors: <a href="mailto:mandyam@qti.qualcomm.com">Giridhar Mandyam</a> (Qualcomm)
 !Contributors: <a href="mailto:mkwst@google.com">Mike West</a> (Google)
-!Contributors: <a href="mailto:Johan.Verrept@vasco.com">Johan Verrept</a> (VASCO Data Security)
 !Contributors: <a href="mailto:jyasskin@google.com">Jeffrey Yasskin</a> (Google)
 group: webauthn
 Issue Tracking: GitHub https://github.com/w3c/webauthn/issues
@@ -4846,6 +4845,7 @@ Kimberly Paulhamus,
 Adam Powers,
 Yaron Sheffer,
 Anne van Kesteren,
+Johan Verrept,
 and
 Boris Zbarsky.