doc: mark --heap-prof and related flags stable

doc/api/cli.md

@@ -1158,9 +1158,14 @@ To allow polyfills to be added,
 
 <!-- YAML
 added: v12.4.0
+changes:
+  - version:
+    - REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/53343
+    description: The `--heap-prof` flags are now stable.
 -->
 
-> Stability: 1 - Experimental
+> Stability: 2 - Stable
 
 Starts the V8 heap profiler on start up, and writes the heap profile to disk
 before exit.
@@ -1181,9 +1186,14 @@ Heap.20190409.202950.15293.0.001.heapprofile
 
 <!-- YAML
 added: v12.4.0
+changes:
+  - version:
+    - REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/53343
+    description: The `--heap-prof` flags are now stable.
 -->
 
-> Stability: 1 - Experimental
+> Stability: 2 - Stable
 
 Specify the directory where the heap profiles generated by `--heap-prof` will
 be placed.
@@ -1195,9 +1205,14 @@ The default value is controlled by the
 
 <!-- YAML
 added: v12.4.0
+changes:
+  - version:
+    - REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/53343
+    description: The `--heap-prof` flags are now stable.
 -->
 
-> Stability: 1 - Experimental
+> Stability: 2 - Stable
 
 Specify the average sampling interval in bytes for the heap profiles generated
 by `--heap-prof`. The default is 512 \* 1024 bytes.
@@ -1206,9 +1221,14 @@ by `--heap-prof`. The default is 512 \* 1024 bytes.
 
 <!-- YAML
 added: v12.4.0
+changes:
+  - version:
+    - REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/53343
+    description: The `--heap-prof` flags are now stable.
 -->
 
-> Stability: 1 - Experimental
+> Stability: 2 - Stable
 
 Specify the file name of the heap profile generated by `--heap-prof`.