fix: Correcting package suffix for main branch

[nickrandolph]

What kind of change does this PR introduce? (Bug fix, feature, docs update, ...) fix: Correcting package suffix for main branch

What is the current behavior? (You can also link to an open issue here) packages are being created with suffix in version number eg 1.0.0-main-a6f7331

What is the new behavior (if this is a feature change)? suffix is dropped for main branch

Does this PR introduce a breaking change? No

Please check if the PR fulfills these requirements

• [ X ] The commit follows our guidelines: https://github.com/serilog/serilog#contribute
• [ N/A ] Tests for the changes have been added (for bug fixes / features)
• [ N/A ] Docs have been added / updated (for bug fixes / features)

Other information: