Fix GenerateOneTimeTokenWebFilter double publish of chain.filter(...)

closes gh-16458

Signed-off-by: Daniel Garnier-Moiroux <git@garnier.wf>

web/src/main/java/org/springframework/security/web/server/authentication/ott/GenerateOneTimeTokenWebFilter.java

@@ -58,7 +58,6 @@ public final class GenerateOneTimeTokenWebFilter implements WebFilter {
 		// @formatter:off
 		return this.matcher.matches(exchange)
 				.filter(ServerWebExchangeMatcher.MatchResult::isMatch)
-				.switchIfEmpty(chain.filter(exchange).then(Mono.empty()))
 				.then(exchange.getFormData())
 				.mapNotNull((data) -> data.getFirst(USERNAME))
 				.switchIfEmpty(chain.filter(exchange).then(Mono.empty()))