The removeWords function only removes specific words. It won't remove phrases like you might expect.
The word clouds are showing n-grams, therefore you are looking remove common n-grams. To do so, use the removeNgrams function. Each phrase should be a 1x2 string array (see the "thou art" and "thou dost" example in the removeNgrams Documentation)
If you are interested in the top n-grams in a bag-of-n-grams model (which you used to create the word cloud), you can use the topkngrams function.
Alternatively (and this is not the preferred approach), you can extract the WordData from a word cloud object:
wc = wordcloud(bag);
wordData = wc.WordData;