Provide script for downloading nightly-6.2 for Windows (swiftlang#138)

Needed for docker-less flow. Also removing nightly-6.1 script

Author: award999

.github/workflows/scripts/windows/swift/install-swift-nightly-6.1.ps1 renamed to .github/workflows/scripts/windows/swift/install-swift-nightly-6.2.ps1

@@ -11,8 +11,8 @@
 ##===----------------------------------------------------------------------===##
 . $PSScriptRoot\install-swift.ps1
 
-$SWIFT_RELEASE_METADATA='http://download.swift.org/swift-6.1-branch/windows10/latest-build.json'
+$SWIFT_RELEASE_METADATA='http://download.swift.org/swift-6.2-branch/windows10/latest-build.json'
 $Release = curl.exe -sL ${SWIFT_RELEASE_METADATA}
-$SWIFT_URL = "https://download.swift.org/swift-6.1-branch/windows10/$($($Release | ConvertFrom-JSON).dir)/$($($Release | ConvertFrom-JSON).download)"
+$SWIFT_URL = "https://download.swift.org/swift-6.2-branch/windows10/$($($Release | ConvertFrom-JSON).dir)/$($($Release | ConvertFrom-JSON).download)"
 
 Install-Swift -Url $SWIFT_URL -Sha256 ""