extends: add type kwarg (#20045)

* extends: add type kwarg

* Flake8 fix

lib/spack/docs/build_systems/perlpackage.rst

@@ -120,8 +120,6 @@ so ``PerlPackage`` contains:
 
    extends('perl')
 
-   depends_on('perl', type=('build', 'run'))
-
 
 If your package requires a specific version of Perl, you should
 specify this.

lib/spack/docs/build_systems/rpackage.rst

@@ -138,7 +138,6 @@ every R package needs this, the ``RPackage`` base class contains:
 .. code-block:: python
 
    extends('r')
-   depends_on('r', type=('build', 'run'))
 
 
 Take a close look at the homepage for ``caret``. If you look at the

lib/spack/docs/build_systems/rubypackage.rst

@@ -113,7 +113,6 @@ the base class contains:
 .. code-block:: python
 
    extends('ruby')
-   depends_on('ruby', type=('build', 'run'))
 
 
 The ``*.gemspec`` file may contain something like: