rpy2 (standard) cannot depend on r (optional)

"make download-for-sdist" tries to download all standard sources
and fails if we depend on a dummy package. Presumably fine since the
r dummy package should only used at configure time.

Author: vbraun

build/pkgs/rpy2/dependencies

@@ -1,4 +1,4 @@
- r cffi tzlocal pytz jinja2 | $(PYTHON_TOOLCHAIN) pycparser $(PYTHON)
+ cffi tzlocal pytz jinja2 | $(PYTHON_TOOLCHAIN) pycparser $(PYTHON)
 
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