[llvm][doc] Add Aarch64 to list of architectures supporting statepoints

Fixes llvm/llvm-project#53655

Differential Revision: https://reviews.llvm.org/D119659

Author: zero9178

llvm/docs/Statepoints.rst

@@ -739,7 +739,7 @@ Supported Architectures
 =======================
 
 Support for statepoint generation requires some code for each backend.
-Today, only X86_64 is supported.
+Today, only Aarch64 and X86_64 are supported.
 
 .. _OpenWork: