Specify that GCS is at Beta level (#379)

main/acle.md

@@ -442,6 +442,8 @@ Armv8.4-A [[ARMARMv84]](#ARMARMv84). Support is added for the Dot Product intrin
 * Changed the status of the SVE2p1 from Alpha to Beta.
 * Added mf8 variants of SME 2.1 intrinsics.
 * Added `svdot[_n_f16_mf8]_fpm` and `svdot[_n_f32_mf8]_fpm`.
+* Added Guarded Control Stack (GCS) at
+  [**Beta**](#current-status-and-anticipated-changes) quality level.
 
 ### References
 
@@ -4927,6 +4929,8 @@ This section describes the intrinsics for the instructions of the
 Guarded Control Stack (GCS) extension. The GCS instructions are present
 in the AArch64 execution state only.
 
+The specification for Guarded Control Stack is at Beta level.
+
 When GCS protection is enabled then function calls also save the return
 address to a separate stack, the GCS, that is checked against the actual
 return address when the function returns. At runtime GCS protection can