improve formatting of variable names in clustering

Author: trevorcampbell

source/clustering.md

@@ -351,7 +351,7 @@ glue('toy-example-clus1-center', toy_example_clus1_center, display=True)
 ```
 
 In the first cluster from the example, there are {glue:text}`clus_rows_glue` data points. These are shown with their cluster center
-(flipper_length_standardized = {glue:text}`mean_flipper_len_std_glue` and bill_length_standardized = {glue:text}`mean_bill_len_std_glue`) highlighted
+(standardized flipper length {glue:text}`mean_flipper_len_std_glue`, standardized bill length {glue:text}`mean_bill_len_std_glue`) highlighted
 in {numref}`toy-example-clus1-center`
 
 :::{glue:figure} toy-example-clus1-center