Update readme to note ia32 is only available in older releases

Author: nicholasbishop

README.md

@@ -7,9 +7,6 @@ The contents of the release tarball look like this:
 x64/shell.efi
 x64/vars.fd
 x64/code.fd
-ia32/shell.efi
-ia32/vars.fd
-ia32/code.fd
 aarch64/vars.fd
 aarch64/code.fd
 aarch64/shell.efi
@@ -21,6 +18,13 @@ loongarch64/code.fd
 loongarch64/shell.efi
 ```
 
+Older releases (`edk2-stable202508` and earlier) also include:
+```
+ia32/shell.efi
+ia32/vars.fd
+ia32/code.fd
+```
+
 [**Latest Release**](https://github.com/rust-osdev/ovmf-prebuilt/releases/latest)
 
 ## License