fix: re-add missing parenthesis to A/B script output

Fixes: fc6a36e

Signed-off-by: Patrick Roy <roypat@amazon.co.uk>

tools/ab_test.py

@@ -285,7 +285,7 @@ def ab_performance_test(
             msg = (
                 f"\033[0;32m[Firecracker A/B-Test Runner]\033[0m A/B-testing shows a change of "
                 f"{format_with_reduced_unit(result.statistic, unit)}, or {result.statistic / old_mean:.2%}, "
-                f"(from {format_with_reduced_unit(old_mean, unit)} to {format_with_reduced_unit(new_mean, unit)}"
+                f"(from {format_with_reduced_unit(old_mean, unit)} to {format_with_reduced_unit(new_mean, unit)}) "
                 f"for metric \033[1m{metric}\033[0m with \033[0;31m\033[1mp={result.pvalue}\033[0m. "
                 f"This means that observing a change of this magnitude or worse, assuming that performance "
                 f"characteristics did not change across the tested commits, has a probability of {result.pvalue:.2%}. "