[MM-61762] Fix errcheck issues in server/channels/app/platform/config_test.go (#29323)

Co-authored-by: Ben Schumacher <ben.schumacher@mattermost.com>

server/.golangci.yml

@@ -101,7 +101,6 @@ issues:
         channels/app/permissions.go|\
         channels/app/permissions_test.go|\
         channels/app/platform/cluster_handlers.go|\
-        channels/app/platform/config_test.go|\
         channels/app/platform/helper_test.go|\
         channels/app/platform/license.go|\
         channels/app/platform/link_cache.go|\

server/channels/app/platform/config_test.go

@@ -88,16 +88,19 @@ func TestConfigSave(t *testing.T) {
 		// Change a random config setting
 		cfg := th.Service.Config().Clone()
 		cfg.ThemeSettings.EnableThemeSelection = model.NewPointer(!*cfg.ThemeSettings.EnableThemeSelection)
-		th.Service.SaveConfig(cfg, false)
+		_, _, appErr := th.Service.SaveConfig(cfg, false)
+		require.Nil(t, appErr)
 		metricsMock.AssertNumberOfCalls(t, "Register", 0)
 
 		// Disable metrics
 		cfg.MetricsSettings.Enable = model.NewPointer(false)
-		th.Service.SaveConfig(cfg, false)
+		_, _, appErr = th.Service.SaveConfig(cfg, false)
+		require.Nil(t, appErr)
 
 		// Change the metrics setting
 		cfg.MetricsSettings.Enable = model.NewPointer(true)
-		th.Service.SaveConfig(cfg, false)
+		_, _, appErr = th.Service.SaveConfig(cfg, false)
+		require.Nil(t, appErr)
 		metricsMock.AssertNumberOfCalls(t, "Register", 1)
 	})
 }
@@ -126,7 +129,8 @@ func TestIsFirstUserAccount(t *testing.T) {
 	}
 
 	// create a session, this should not affect IsFirstUserAccount
-	th.Service.sessionCache.SetWithDefaultExpiry("mock_session", 1)
+	err := th.Service.sessionCache.SetWithDefaultExpiry("mock_session", 1)
+	require.NoError(t, err)
 
 	for _, te := range tests {
 		t.Run(te.name, func(t *testing.T) {