[rust] Fails to extract benchmark result

I assume there is a problem with the regex in https://github.com/rhysd/github-action-benchmark/blob/master/src/extract.ts#L181

My benchmark results look like this:
```
test core::builder::graph::tests::bench_create_mid_graph ... bench: 4,720,415 ns/iter (+/- 498,541)
test core::builder::graph::tests::bench_create_small_graph ... bench: 40,447 ns/iter (+/- 1,061)
```
Please note the colons in the name. The regex `/^test ([\w/]+)\s+\.\.\. bench:\s+([0-9,]+) ns\/iter \(\+\/- ([0-9,]+)\)$/;` doesn't consider the colons. The fix is probably easy: `[\w/:]`