multiple pages: normalize regular expression instead of regex, regexp or pattern (#5830)

pages/osx/rename.md

@@ -1,6 +1,6 @@
 # rename
 
-> Rename a file or group of files with a regex.
+> Rename a file or group of files with a regular expression.
 
 - Replace `from` with `to` in the filenames of the specified files:
 

pages/osx/sed.md

@@ -9,7 +9,7 @@
 
 - Replace all occurrences of an extended regular expression in a file:
 
-`sed -E 's/{{regex}}/{{replace}}/g' {{filename}}`
+`sed -E 's/{{regular_expression}}/{{replace}}/g' {{filename}}`
 
 - Replace all occurrences of a string [i]n a file, overwriting the file (i.e. in-place):