chore: drop net6.0/net7.0 from Playwright.CLI (#3054)

Author: mxschmitt

src/Playwright.CLI/Playwright.CLI.csproj

@@ -6,7 +6,7 @@
     <Summary>The Playwright CLI dotnet tool.</Summary>
     <Description>Playwright enables reliable end-to-end testing for modern web apps. It is built to enable cross-browser web automation that is ever-green, capable, reliable and fast. Learn more at https://playwright.dev/dotnet/.</Description>
     <PackageIcon>icon.png</PackageIcon>
-    <TargetFrameworks>net6.0;net7.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>net8.0</TargetFrameworks>
     <PublishRepositoryUrl>true</PublishRepositoryUrl>
     <RunWithWarnings>true</RunWithWarnings>
     <RootNamespace>Microsoft.Playwright.CLI</RootNamespace>