Make title of bash command guides more consistent (#18814)

* Fix typo

* Fix typo

* Fix typo

* Fix typo

client/src/guide/english/bash/bash-cat/index.md

@@ -1,8 +1,8 @@
 ---
-title: Bash Cat
+title: Bash cat
 ---
 
-## Bash Cat
+## Bash command: cat
 
 Cat is one of the most frequently used commands in Unix operating systems.
 

client/src/guide/english/bash/bash-head/index.md

@@ -1,5 +1,5 @@
 ---
-title: Bash Head
+title: Bash head
 ---
 
 ## Bash command: head

client/src/guide/english/bash/bash-ls/index.md

@@ -2,7 +2,7 @@
 title: Bash ls
 ---
 
-## Bash ls
+## Bash command: ls
 
 `ls` is a command on Unix-like operating systems to list contents of a directory, for example folder and file names.
 

client/src/guide/english/bash/bash-man/index.md

@@ -2,7 +2,7 @@
 title: Bash Man
 ---
 
-## Man
+## Bash command: man
 
 Man, the abbreviation of **man**ual, is a bash command used to display on-line reference manuals of the given command.
 
@@ -29,4 +29,4 @@ man ls
 
 #### More information:
 
-* Wikipedia: https://en.wikipedia.org/wiki/Man_page
+* Wikipedia: https://en.wikipedia.org/wiki/Man_page