Remove process.on('multipleResolves') listeners

The 'multipleResolves' process event was removed in Node.js 25 (DEP0160) because it did not work with the V8 promise combinators, which left it of little use. Node.js offers no replacement and never emits the event, so registering a listener for it is dead code and the registration is removed. The handler itself is left in place, since it may be referenced elsewhere. Only a registration written as its own statement is removed; one whose result is used, such as a chained or assigned call, is left alone.