fix: cross-platform compatibility for sf-deploy and sf-dry-run scripts

- Fixed bash syntax error on Linux: 1 -> 0
- The problematic syntax worked on macOS but failed on Linux with 'bad substitution' error
- Now compatible with both Linux and macOS bash versions
- Tested on Ubuntu Linux with bash 5.2.21

sf-deploy

@@ -127,7 +127,7 @@ done
 [[ -n "$ORG" ]] && CMD+=(--target-org "$ORG")
 
 # tests
-if [[ ${#TESTS_ARR[@]:-0} -gt 0 ]]; then
+if [[ ${#TESTS_ARR[@]} -gt 0 ]]; then
   CMD+=(--test-level RunSpecifiedTests)
   for T in "${TESTS_ARR[@]}"; do
     [[ -n "$T" ]] && CMD+=(--tests "$T")