Update README.md

Correct misinformation about platforms.

README.md

@@ -1,20 +1,13 @@
 # rasterio-wheels
 
-Rasterio wheel builds based on https://github.com/multi-build/multibuild.
-
 This project builds the rasterio binary distributions that are uploaded to
 PyPI. Those distributions, or "wheels", include a GDAL shared library and other
 shared libraries supporting many, but not all, of GDAL's format drivers. If you
 need the rarely used formats and compressors not found in these wheels, you may
 find them in the conda-forge conda channel, or in Docker images published by
 the GDAL project.
 
-Wheels for x86_64 manylinux2014 and macos Pythons 3.7-3.10 are built by GitHub
-Actions.
-
-Wheels for aarch64 linux and arm64 macos are complicated by limited
-availability of build instances and cross-compilation issues within GDAL's
-dependencies. See the issue tracker for details.
+Wheels for manylinux2014_x86_64, macos_10_15_x86_64, and win_amd64 are built by GitHub
+Actions. Wheels for macosx_11_0_arm64 are built by Cirrus CI.
 
-Wheels for windows are not available. We don't have enough Windows experience
-in this project yet.
+Other platforms are out of scope at this time.