Fully deprecate CallsEnabled feature flag (#27826)

Co-authored-by: Mattermost Build <build@mattermost.com>

server/channels/app/plugin_test.go

@@ -1378,62 +1378,6 @@ func TestGetPluginStateOverride(t *testing.T) {
 		require.False(t, value)
 	})
 
-	t.Run("calls override", func(t *testing.T) {
-		t.Run("on-prem", func(t *testing.T) {
-			overrides, value := th.App.ch.getPluginStateOverride("com.mattermost.calls")
-			require.False(t, overrides)
-			require.False(t, value)
-		})
-
-		t.Run("Cloud, without enabled flag", func(t *testing.T) {
-			os.Setenv("MM_CLOUD_INSTALLATION_ID", "test")
-			defer os.Unsetenv("MM_CLOUD_INSTALLATION_ID")
-			overrides, value := th.App.ch.getPluginStateOverride("com.mattermost.calls")
-			require.False(t, overrides)
-			require.False(t, value)
-		})
-
-		t.Run("Cloud, with enabled flag set to true", func(t *testing.T) {
-			os.Setenv("MM_CLOUD_INSTALLATION_ID", "test")
-			defer os.Unsetenv("MM_CLOUD_INSTALLATION_ID")
-			os.Setenv("MM_FEATUREFLAGS_CALLSENABLED", "true")
-			defer os.Unsetenv("MM_FEATUREFLAGS_CALLSENABLED")
-
-			th2 := Setup(t)
-			defer th2.TearDown()
-
-			overrides, value := th2.App.ch.getPluginStateOverride("com.mattermost.calls")
-			require.False(t, overrides)
-			require.False(t, value)
-		})
-
-		t.Run("Cloud, with enabled flag set to false", func(t *testing.T) {
-			os.Setenv("MM_CLOUD_INSTALLATION_ID", "test")
-			defer os.Unsetenv("MM_CLOUD_INSTALLATION_ID")
-			os.Setenv("MM_FEATUREFLAGS_CALLSENABLED", "false")
-			defer os.Unsetenv("MM_FEATUREFLAGS_CALLSENABLED")
-
-			th2 := Setup(t)
-			defer th2.TearDown()
-
-			overrides, value := th2.App.ch.getPluginStateOverride("com.mattermost.calls")
-			require.True(t, overrides)
-			require.False(t, value)
-		})
-
-		t.Run("On-prem, with enabled flag set to false", func(t *testing.T) {
-			os.Setenv("MM_FEATUREFLAGS_CALLSENABLED", "false")
-			defer os.Unsetenv("MM_FEATUREFLAGS_CALLSENABLED")
-
-			th2 := Setup(t)
-			defer th2.TearDown()
-
-			overrides, value := th2.App.ch.getPluginStateOverride("com.mattermost.calls")
-			require.True(t, overrides)
-			require.False(t, value)
-		})
-	})
-
 	t.Run("apps override", func(t *testing.T) {
 		t.Run("without enabled flag", func(t *testing.T) {
 			overrides, value := th.App.ch.getPluginStateOverride("com.mattermost.apps")