Sync qxmlstream.g with qxmlstreamparser_p.h [1/2]: switched lines

Amends 366bdcde97.

Pick-to: 6.3 6.2 5.15
Change-Id: Id18da42b15c8095154408f58bb5e0c5f0d31739b
Reviewed-by: Sona Kurazyan <sona.kurazyan@qt.io>

src/corelib/serialization/qxmlstream.g

@@ -1301,9 +1301,9 @@ etag ::= LANGLE SLASH qname space_opt RANGLE;
             Tag tag = tagStack_pop();
 
             namespaceUri = tag.namespaceDeclaration.namespaceUri;
+            prefix = tag.namespaceDeclaration.prefix;
             name = tag.name;
             qualifiedName = tag.qualifiedName;
-            prefix = tag.namespaceDeclaration.prefix;
             if (qualifiedName != symName(3))
                 raiseWellFormedError(QXmlStream::tr("Opening and ending tag mismatch."));
         } break;