Update B to b for scrolling back by one page in the man pager in …

…02-filedir.md

episodes/02-filedir.md

@@ -304,7 +304,7 @@ of the `ls` command and its options.
 
 To navigate through the `man` pages,
 you may use <kbd>↑</kbd> and <kbd>↓</kbd> to move line-by-line,
-or try <kbd>B</kbd> and <kbd>Spacebar</kbd> to skip up and down by a full page.
+or try <kbd>b</kbd> and <kbd>Spacebar</kbd> to skip up and down by a full page.
 To search for a character or word in the `man` pages,
 use <kbd>/</kbd> followed by the character or word you are searching for.
 Sometimes a search will result in multiple hits.