You can still do it.
Just click the layer with your text, then right click and choose "rasterzerize layer" (I know I can't spell it). Then go to Image > Adjustments > Desaturate.
If you have it set so the text is see through, then hold control on your keyboard, and click the text layer, this will make it load the selection of the text. Then click ony your background layer, and go to Image > Adjustments > Desaturate.
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