Restore TomcatHeadersAdapter.clear() behavior

This commit restores the original behavior of the clear() method in
TomcatHeadersAdapter by delegating to
org.apache.tomcat.util.http.MimeHeaders.recycle(), which aligns with
the memory efficiency goals documented in the class-level Javadoc for
MimeHeaders.

See gh-33916
Closes gh-34092

spring-web/src/main/java/org/springframework/http/server/reactive/TomcatHeadersAdapter.java

@@ -163,9 +163,7 @@ class TomcatHeadersAdapter implements MultiValueMap<String, String> {
 
 	@Override
 	public void clear() {
-		while (this.headers.size() > 0) {
-			this.headers.removeHeader(0);
-		}
+		this.headers.recycle();
 	}
 
 	@Override