Removed pipe in temp_del() function

Per comment [here](https://github.com/bats-core/bats-core/issues/276#issuecomment-619464618) by @Vampire, piped commands aren't necessary when main command has arguments that cover the use case.
diff --git a/src/temp.bash b/src/temp.bash
index 21b88e8..a393bd2 100755
--- a/src/temp.bash
+++ b/src/temp.bash
@@ -172,7 +172,7 @@
 
   # 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' \