Bug #533: Update .NET version in CONTRIBUTING.md #686

Job	Run time
Set version number	21s
Run tests (Basic_tests)	30s
Run tests (SqlServer)	4m 11s
Run tests (PostgreSQL)	1m 49s
Run tests (MariaDB)	1m 12s
Run tests (Sqlite)	46s
Run tests (Oracle)	10m 24s
Build Nuget (grate.core)	34s
Build .NET Core (global) tool	44s
Build cli (win-x64)	34s
Build Nuget (grate.mariadb)	40s
Build and push docker image	0s
Build cli (win-x86)	43s
Build Nuget (grate.oracle)	2m 31s
Build cli (win-arm64)	58s
Build cli (osx-arm64)	54s
Build Nuget (grate.postgresql)	25s
Build cli (linux-musl-x64)	43s
Build Nuget (grate.sqlite)	35s
Build cli (linux-musl-arm64)	55s
Build Nuget (grate.sqlserver)	31s
Build cli (linux-x64)	53s
Build cli (linux-arm64)	1m 7s
Build cli (osx-x64)	1m 5s
Build MSI	0s
Build Debian package	0s
	33m 5s

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