Update Zcherilevels status

This extensions is stable with LVLBITS=1 and undergoing evaluation.

src/introduction.adoc

@@ -109,7 +109,7 @@ CAUTION: The extension names are provisional and subject to change.
 |<<lr_sc_bh_ext,     {lr_sc_bh_ext_name}>>      | Stable    | This extension is a candidate for freezing
 |<<cheri_pte_ext,    {cheri_pte_ext_name}>>     | Stabilizing | This extension is a candidate for freeze, software evaluation currently ongoing
 |<<tid_ext,          {tid_ext_name}>>           | Stabilizing | This extension is a candidate for freeze, software evaluation currently ongoing
-|<<cheri_levels_ext, {cheri_levels_ext_name}>> with `LVLBITS=1` | Prototype | This extension is a prototype, software is being developed to use it to increase the maturity level.
+|<<cheri_levels_ext, {cheri_levels_ext_name}>> with `LVLBITS=1` | Stabilizing | This extension is a candidate for freeze, software evaluation currently ongoing
 |==============================================================================
 
 {cheri_base_ext_name} is defined as the base extension which all CHERI RISC-V