Update recording-changes.asc

Added note about git diff --staged and git diff --cached being synonyms

Author: mrlucmorin

book/02-git-basics/sections/recording-changes.asc

@@ -345,7 +345,7 @@ index 643e24f..87f08c8 100644
 +# test line
 ----
 
-and `git diff --cached` to see what you've staged so far:
+and `git diff --cached` to see what you've staged so far (--staged and --cached are synonyms):
 
 [source,console]
 ----