Refactor: improve consistency of the term "directory".

This commit changes the term "folder" to "directory" in every
instance where the first is used in an example description, but the
second is used in the example code, and vice versa.

pages/common/rm.md

@@ -8,11 +8,11 @@
 
 - Recursively remove a directory and all its subdirectories:
 
-`rm -r {{path/to/folder}}`
+`rm -r {{path/to/directory}}`
 
 - Forcibly remove a directory, without prompting for confirmation or showing error messages:
 
-`rm -rf {{path/to/folder}}`
+`rm -rf {{path/to/directory}}`
 
 - Interactively remove multiple files, with a prompt before every removal:
 
@@ -20,4 +20,4 @@
 
 - Remove files in verbose mode, printing a message for each removed file:
 
-`rm -v {{path/to/folder/*}}`
+`rm -v {{path/to/directory/*}}`