message: core: add missing "and"
  This fixes a typo in the `tracing-core` rustdoc. Thanks
diff: @@ -237,7 +237,7 @@ impl Current {
  /// Returns `true` if the `Subscriber` that constructed this `Current` tracks a
  /// current span.
  ///
  - /// If this returns `true`, if [`id`], [`metadata`], or [`into_inner`]
  + /// If this returns `true` and [`id`], [`metadata`], or [`into_inner`]
  /// return `None`, that indicates that we are currently known to *not* be
  /// inside a span. If this returns `false`, those methods will also return
  /// `None`, but in this case, that is because the subscriber does not keep
  