message: tracing: fix incorrect `follows_from` bounds
  Authored-By: David Barsky
diff: @@ -720,10 +720,51 @@ impl Span {
  ///
  /// If this span is disabled, or the resulting follows-from relationship
  /// would be invalid, this function will do nothing.
  - pub fn follows_from(&self, from: impl for<'a> Into<Option<&'a Id>>) -> &Self {
  + ///
  + /// # Examples
  + ///
  + /// Setting a `follows_from` relationship with a `Span`:
  + /// ```
  + /// # use tracing::{span, Id, Level, Span};
  + /// # fn main() {
  + /// let span1 = span!(Level::INFO, "span_1");
  + /// let span2 = span!(Level::DEBUG, "span_2");
  + /// span2.follows_from(span1);
  + /// # }
  + /// ```
  + ///
  + /// Setting a `follows_from` relationship with the current span:
  + /// ```
  + /// # use tracing::{span, Id, Level, Span};
  + /// # fn main() {
  + /// let span = span!(Level::INFO, "hello!");
  + /// span.follows_from(Span::current());
  + /// # }
  + /// ```
  + ///
  + /// Setting a `follows_from` relationship with a `Span` reference:
  + /// ```
  + /// # use tracing::{span, Id, Level, Span};
  + /// # fn main() {
  + /// let span = span!(Level::INFO, "hello!");
  + /// let curr = Span::current();
  + /// span.follows_from(&curr);
  + /// # }
  + /// ```
  + ///
  + /// Setting a `follows_from` relationship with an `Id`:
  + /// ```
  + /// # use tracing::{span, Id, Level, Span};
  + /// # fn main() {
  + /// let span = span!(Level::INFO, "hello!");
  + /// let id = span.id();
  + /// span.follows_from(id);
  + /// # }
  + /// ```
  + pub fn follows_from(&self, from: impl Into<Option<Id>>) -> &Self {
  if let Some(ref inner) = self.inner {
  if let Some(from) = from.into() {
  - inner.follows_from(from);
  + inner.follows_from(&from);
  }
  }
  self
  