bash: adjust example to read from file into array (#2187)

* use `$()` rather than deprecated ``
* illustrate shortcut for builtin read of file without `cat`
* don't imply this reads lines, it will split into words by default

perhaps the cheatsheet should have a section on IFS, but that's
off-topic for this patch.

Co-authored-by: Rico Sta. Cruz <rstacruz@users.noreply.github.com>

bash.md

@@ -510,7 +510,7 @@ Fruits=( "${Fruits[@]/Ap*/}" )          # Remove by regex match
 unset Fruits[2]                         # Remove one item
 Fruits=("${Fruits[@]}")                 # Duplicate
 Fruits=("${Fruits[@]}" "${Veggies[@]}") # Concatenate
-lines=(`cat "logfile"`)                 # Read from file
+words=($(< datafile))                   # From file (split by IFS)
 ```
 
 ### Iteration