WARNING require.twbs/bootstrap : exact version constraints (4.3.1) should be avoided if the package follows semantic versioning

I use Laravel Framework version 5.8 I try command composer diag, then I get warning :

Checking composer.json: WARNING require.twbs/bootstrap : exact version constraints (4.3.1) should be avoided if the package follows semantic versioning

What best way to fix this? And what this warning a big problem? Please explain to me, thank you~

via Chebli Mohamed