README.org: don't show WSL2 badge

Avoid false advertising

README.org

@@ -10,7 +10,6 @@
 [[https://www.djcbsoftware.nl/code/mu/mu4e/Installation.html#Dependencies-for-Debian_002fUbuntu][https://img.shields.io/badge/Platform-Linux-2e8b57?logo=linux&.svg]]
 [[https://www.djcbsoftware.nl/code/mu/mu4e/Installation.html#Building-from-a-release-tarball-1][https://img.shields.io/badge/Platform-FreeBSD-8b3a3a?logo=freebsd&logoColor=c32136&.svg]]
 [[https://formulae.brew.sh/formula/mu#default][https://img.shields.io/badge/Platform-macOS-101010?logo=apple&logoColor=ffffff&.svg]]
-https://img.shields.io/badge/Platform-WSL2%20(experimental)-blue.svg
 
  [ *Note*: you are looking at the *development* branch, which is where new code is
  being developed and tested, and which may occasionally break. Distributions and