message: Clarify dependencies documentation
  The snippet:
  ```
  ... but not `2.0`. `0.0.x` is not considered ...
  ```
  Looks very similar to `... but not 2.0.0.0.x is not considered ...`, when rendered, which is confusing.
  This adds a couple words to clarify.
diff: @@ -31,8 +31,8 @@ An update is allowed if the new version number does not modify the left-most
  non-zero digit in the major, minor, patch grouping. In this case, if we ran
  `cargo update -p time`, cargo would update us to version `0.1.13` if it was
  available, but would not update us to `0.2.0`. If instead we had specified the
  -version string as `^1.0`, cargo would update to `1.1` but not `2.0`. `0.0.x` is
  -not considered compatible with any other version.
  +version string as `^1.0`, cargo would update to `1.1` but not `2.0`. The version
  +`0.0.x` is not considered compatible with any other version.
  Here are some more examples of caret requirements and the versions that would
  be allowed with them:
  