Changed the condition of _RefitMSBuildVersionCheck

[dannythunder]

What kind of change does this PR introduce? [BUG] Unable to build Refit with MSBuild >= 17.x #1387

What is the current behavior? Can't evaluate if build versions is OK

What is the new behavior? Changed the logic how they evaluate

What might this PR break? Nothing i suppose

Please check if the PR fulfills these requirements

• [ ] ~~Tests for the changes have been added (for bug fixes / features)~~
• [ ] ~~Docs have been added / updated (for bug fixes / features)~~

Other information: Somehow the Condition thinks 1 is bigger than 2, hence the ! (not) infront of the condition. Guess I lack some understanding about .target and such.