docs: drop the obsolete Rosetta2 guidance for Apple silicon

bioconda has shipped native osx-arm64 builds since simpleaf 0.18.0, piscem
0.10.2, and alevin-fry 0.11.0, plus linux-aarch64 for all three, so telling
Apple-silicon users to install under x86 emulation has been wrong for a while
and now steers them onto a slower path for no reason. The "all x86 (Linux or
Mac) users" framing on the conda recommendation is stale for the same reason.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VhyNvEWUgY8ALVacdJHxVJ

Author: rob-p

docs-site/src/content/docs/installation.md

@@ -10,12 +10,12 @@ This release requires **piscem >= 0.22.0** and **alevin-fry >= 0.17.0**. These a
 
 ## Recommended: installing from conda
 
-We recommend all x86 (Linux or Mac) users to install `simpleaf` from bioconda, because all its dependencies are also available on conda, and will be automatically installed (except `piscem`) when installing `simpleaf`.
+We recommend that Linux and macOS users install `simpleaf` from bioconda, because all its dependencies are also available on conda, and will be automatically installed (except `piscem`) when installing `simpleaf`.
 
 ```sh
 conda install simpleaf piscem -c bioconda -c conda-forge
 ```
-**For Apple-silicon computers**, for example those with an Apple M-series chip, simpleaf should be installed under the x86 emulation layer, in other words, in shell with Rosetta2 enabled. See [this](https://combine-lab.github.io/alevin-fry-tutorials/2023/simpleaf-piscem/#:~:text=Attention%20Apple%20silicon%20computer%20users%3A) for details. Furthermore, if one would like to use `piscem` on apple silicon, one has to either download the [pre-built piscem executable](https://github.com/COMBINE-lab/piscem/releases) or build piscem from source **in the native shell (with Rosetta2 disabled)** using the commands described [here](https://github.com/COMBINE-lab/piscem#building). Then, piscem can be executed from both Rosetta2 enabled and disabled shell.
+**Apple-silicon and ARM users** need no special handling. bioconda ships native `osx-arm64` and `linux-aarch64` packages for `simpleaf`, `piscem`, and `alevin-fry`, so the command above works as-is in a native shell. Rosetta2 is not required, and installing under emulation is no longer recommended.
 
 ## Installing with cargo