Remove metadata from `safeVersion`

[iamacook]

Context / issue

L2 Safe contract versions are returned with +L2 metadata from the gateway. (Circles also contains +Circles metadata).

1.3.0+L2 is currently an invalid version. It won't allow usage of the SDK.

Proposed solution

Using semver for version retrieval as it strips metadata.

Alternatives

Metadata is marked with + by default. It can be remove manually:

  const [noMetadataVersion] = safeVersion.split('+')