DOC: update `libmambapy` vs `virtualenv` note, now we have `rattler`

[lucascolley]

asv/docs/source/installing.rst

Lines 42 to 51 in 1aa1c73

	.. note::
	``libmambapy`` is the fastest for situations where non-pythonic
	dependencies are required. Anaconda or miniconda is slower but
	still preferred if the project involves a lot of compiled C/C++
	extensions and are available in the ``conda`` repository, since
	``conda`` will be able to fetch precompiled binaries for these
	dependencies in many cases. Using ``virtualenv``, dependencies
	without precompiled wheels usually have to be compiled every
	time the environments are set up.

cc @HaoZeke