Remove the additional '|' syntax for toolchain requirements. ...

- '|' seems confusing, given that it is used as a logical AND
- Dependency already supports specifying an arbitrary range and this is the only meaningful use for '|'
- Keeps the possibility open to use '|' as a logical OR in a later version
- Rewords the change log entry and adds a link to the DUB documentation

toolchainRequirements recipe support