Removed pipe in temp_del() function

Per comment [here](bats-core/bats-core#276 (comment)) by @Vampire, piped commands aren't necessary when main command has arguments that cover the use case.

src/temp.bash

@@ -172,7 +172,7 @@ temp_del() {
 
   # Delete directory.
   local result
-  result="$(yes | rm -r -- "$path" 2>&1)"
+  result="$(rm -rf -- "$path" 2>&1)"
   if (( $? )); then
     echo "$result" \
       | batslib_decorate 'ERROR: temp_del' \