Use replaceChildren in StreamActions.update

While processing `<turbo-stream action="update">` elements, Turbo
combines two steps:

1. sets [`innerHTML = ""`][innerHTML]
2. call [`append(this.templateContent)`][append]

Modern `Element` implementations provide a [replaceChildren][] method
that effectively combines these two steps into a single, atomic
operation.

The `Element.replaceChildren()` method [isn't supported by Internet
Explorer][replaceChildren compatibility], but the `Element.append()`
method that it replaces [has the same incompatibility issues][append
compatibility].

[innerHTML]: https://developer.mozilla.org/en-US/docs/Web/API/Element/innerHTML
[append]: https://developer.mozilla.org/en-US/docs/Web/API/Element/append
[append compatibility]: https://developer.mozilla.org/en-US/docs/Web/API/Element/append#browser_compatibility
[replaceChildren]: https://developer.mozilla.org/en-US/docs/Web/API/Element/replaceChildren
[replaceChildren compatibility]: https://developer.mozilla.org/en-US/docs/Web/API/Element/replaceChildren#browser_compatibility

src/core/streams/stream_actions.ts

@@ -28,9 +28,6 @@ export const StreamActions: { [action: string]: (this: StreamElement) => void }
   },
 
   update() {
-    this.targetElements.forEach(e => { 
-      e.innerHTML = ""
-      e.append(this.templateContent)
-    })
+    this.targetElements.forEach(e => e.replaceChildren(this.templateContent))
   }
 }