Remove test cases that point to a four digit versioning scheme

[divyenduz]

We recently found out that the four-digit versioning we agreed to (#121 (comment)) is not possible as vsce/npm don't work with it.

This PR tracks the removal of the outdated code/test cases that are based on the 4 digit extension assumption as these test cases/references may be misleading.

We need a new versioning schema for Prisma CLI patches and extension only publishing.

That is being tracked in these issues:

#240
#143

P.S. and also remove pre GA test cases for extension version as they are no longer needed.