Bug 1629316 - Replace MOZ_MUST_USE with [[nodiscard]] in accessible. r=Jamie

Differential Revision: https://phabricator.services.mozilla.com/D70630

--HG--
extra : moz-landing-system : lando

accessible/ipc/DocAccessibleParent.h

@@ -296,7 +296,7 @@ class DocAccessibleParent : public ProxyAccessible,
   uint32_t AddSubtree(ProxyAccessible* aParent,
                       const nsTArray<AccessibleData>& aNewTree, uint32_t aIdx,
                       uint32_t aIdxInParent);
-  MOZ_MUST_USE bool CheckDocTree() const;
+  [[nodiscard]] bool CheckDocTree() const;
   xpcAccessibleGeneric* GetXPCAccessible(ProxyAccessible* aProxy);
 
   nsTArray<uint64_t> mChildDocs;

accessible/windows/msaa/AccessibleWrap.h

@@ -186,7 +186,7 @@ class AccessibleWrap : public Accessible,
   /**
    * Find an accessible by the given child ID in cached documents.
    */
-  MOZ_MUST_USE already_AddRefed<IAccessible> GetIAccessibleFor(
+  [[nodiscard]] already_AddRefed<IAccessible> GetIAccessibleFor(
       const VARIANT& aVarChild, bool* aIsDefunct);
 
   virtual void GetNativeInterface(void** aOutAccessible) override;
@@ -221,7 +221,7 @@ class AccessibleWrap : public Accessible,
   /**
    * Find a remote accessible by the given child ID.
    */
-  MOZ_MUST_USE already_AddRefed<IAccessible> GetRemoteIAccessibleFor(
+  [[nodiscard]] already_AddRefed<IAccessible> GetRemoteIAccessibleFor(
       const VARIANT& aVarChild);
 
   /**