docs: Pin link to pre-built pvmfw.img to last commit

Instead of pointing to master, pin the link to the U-Boot-based
pvmfw.img pre-built to the parent of the commit which removed it,
08deac98acef ("pvmfw: Delete U-Boot-based pvmfw.img prebuilt").

note: The documentation for Android 13 should still point to it as the
      replacement (intended for Android 14) is not guaranteed to be
      ABI-compatible with the pre-built.

Bug: 253397262
Test: -
Change-Id: I6bc440a01df386816278d328a3eb4e4f3290e5df
diff --git a/docs/getting_started/index.md b/docs/getting_started/index.md
index 357f980..a354339 100644
--- a/docs/getting_started/index.md
+++ b/docs/getting_started/index.md
@@ -66,7 +66,7 @@
 ```
 
 Finally, if the `pvmfw` partition has been corrupted, both slots may be flashed
-using the [`pvmfw.img` pre-built](https://android.googlesource.com/platform/packages/modules/Virtualization/+/refs/heads/master/pvmfw/pvmfw.img)
+using the [`pvmfw.img` pre-built](https://android.googlesource.com/platform/packages/modules/Virtualization/+/08deac98acefd62e222edfa374d5292458cf97eb%5E/pvmfw/pvmfw.img)
 as long as the bootloader remains unlocked. Otherwise, a fresh install of
 Android 13 followed by the manual steps above for flashing the `other` slot
 should be used as a last resort.