Fix lint issue

vector/src/main/res/layout/bottom_sheet_space_settings.xml

@@ -49,6 +49,7 @@
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             android:layout_marginEnd="8dp"
+            android:contentDescription="@string/a11y_beta"
             android:src="@drawable/ic_beta_pill"
             app:layout_constraintEnd_toEndOf="parent"
             app:layout_constraintTop_toTopOf="parent" />

vector/src/main/res/layout/fragment_matrix_to_room_space_card.xml

@@ -33,7 +33,7 @@
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             android:layout_marginTop="@dimen/layout_vertical_margin_big"
-            android:importantForAccessibility="no"
+            android:contentDescription="@string/a11y_beta"
             android:src="@drawable/ic_beta_pill"
             android:visibility="gone"
             app:layout_constraintEnd_toEndOf="parent"

vector/src/main/res/values/strings.xml

@@ -2294,6 +2294,7 @@
     <string name="a11y_show_password">Show password</string>
     <string name="a11y_hide_password">Hide password</string>
     <string name="a11y_jump_to_bottom">Jump to bottom</string>
+    <string name="a11y_beta">This feature is undergoing beta testing</string>
 
     <!-- Read receipts list a11y -->
     <plurals name="two_and_some_others_read">