test(basics): Replace push_scope (getsentry#3353)

Most of the `push_scope` usages in `test_basics.py` need to stay, as
they test functionality specific to `push_scope`.

However, in `test_scope_event_processor_order`, the `push_scope` can
be replaced with `new_scope`. We make this replacement here.

Ref: getsentry#3345

tests/test_basics.py

@@ -22,6 +22,7 @@
     last_event_id,
     add_breadcrumb,
     isolation_scope,
+    new_scope,
     Hub,
     Scope,
 )
@@ -606,14 +607,14 @@ def before_send(event, hint):
     sentry_init(debug=True, before_send=before_send)
     events = capture_events()
 
-    with push_scope() as scope:
+    with new_scope() as scope:
 
         @scope.add_event_processor
         def foo(event, hint):
             event["message"] += "foo"
             return event
 
-        with push_scope() as scope:
+        with new_scope() as scope:
 
             @scope.add_event_processor
             def bar(event, hint):