Have generic updater support numbers without breaks

I'm looking to support go major versioning where in a go.mod file last part of the module path must be the major version with `v` prefixed.

```
// x-release-please-start-major
module github.com/jeremytchang/test-release-please-go/go/v4

// x-release-please-end

go 1.14
```

Currently, the generic updater can only update the major version if it is a number by itself. The regex: `/\b\d+\b/` https://github.com/googleapis/release-please/blob/c97598c137b5018c76f5d62137e277b991f4bfa3/src/updaters/generic.ts#L21

What do you all think of simplifying it to just `/\d+/` [example](https://regex101.com/r/5DXSiv/1) or `/\bv?d+\b/` [example](https://regex101.com/r/0CgbEy/1) or something along those lines.

It would still support the current use case. Though it could break current implementations that have a line like `blah/12/blah 12` where both 12's will be replaced.