The document is in Frozen state now. Update the spec to relfect that.

Signed-off-by: Atish Patra <atishp@rivosinc.com>

riscv-ffh.adoc

@@ -5,7 +5,7 @@
 // Pull in variable with revision info
 :revnumber: 1234
 :revdate: 2023-01-01
-:revremark: This document is stable. Assume anything could still change, but limited change should be expected. Visit http://riscv.org/spec-state for further details. 
+:revremark: This document is Frozen. Change is extremely unlikely. A high threshold will be used, and a change will only occur because of some truly critical issue being identified during the public review cycle. Any other desired or needed changes can be the subject of a follow-on new extension. Visit http://riscv.org/spec-state for further details.
 :url-riscv: http://riscv.org
 :doctype: book
 :preface-title: Preamble
@@ -42,12 +42,12 @@ endif::[]
 
 // Preamble
 [WARNING]
-.This document is in the link:http://riscv.org/spec-state[Development state]
-====
-Assume everything can change. This draft specification will change before
-being accepted as standard, so implementations made to this draft
-specification will likely not conform to the future standard.
-====
+.This document is in the link:http://riscv.org/spec-state[Frozen state]
+===
+Change is extremely unlikely. A high threshold will be used, and a change will
+only occur because of some truly critical issue being identified during the
+public review cycle. Any other desired or needed changes can be the subject of
+a follow-on new extension.
 
 [preface]
 == Copyright and license information