Stabilize GetAll in TextMap Extract (#4472)

Fixes #4471 

## Changes

Removes "In Development" status notice for `GetAll`

---------

Co-authored-by: Robert Pająk <[email protected]>

Author: jamesmoessis

CHANGELOG.md

@@ -11,6 +11,8 @@ release.
 
 - Add context propagation through Environment Variables specification.
     ([#4454](https://github.com/open-telemetry/opentelemetry-specification/pull/4454))
+- On Propagators API, stabilize `GetAll` on the `TextMap` Extract.
+    ([#4472](https://github.com/open-telemetry/opentelemetry-specification/pull/4472))
 
 ### Traces
 

specification/context/api-propagators.md

@@ -1,6 +1,6 @@
 # Propagators API
 
-**Status**: [Stable](../document-status.md), except where otherwise specified.
+**Status**: [Stable](../document-status.md)
 
 <details>
 <summary>Table of Contents</summary>
@@ -233,8 +233,6 @@ The Get function is responsible for handling case sensitivity. If the getter is
 
 ##### GetAll
 
-**Status**: [Development](../document-status.md)
-
 For many language implementations, the `GetAll` function will be added after the stable release of `Getter`.
 For these languages, requiring implementations of `Getter` to include `GetAll` constitutes a breaking change
 since instrumentation which previously functioned would fail. Language implementations should be cognizant