fix(http): use params without RequestOptions (#14101)

`params` has been introduced in 4.0.0-beta.0

Before:

    http.get(url, new RequestOptions({params: searchParams}))

After:

    http.get(url, {params: searchParams})

Fixes #14100

PR Close #14101

modules/@angular/http/src/http.ts

@@ -28,6 +28,7 @@ function mergeOptions(
       method: providedOpts.method || method,
       url: providedOpts.url || url,
       search: providedOpts.search,
+      params: providedOpts.params,
       headers: providedOpts.headers,
       body: providedOpts.body,
       withCredentials: providedOpts.withCredentials,