Update graph-connector-agent.md

Best practice is for authentication certificate to use at least SHA256, default is SHA1.  https://learn.microsoft.com/en-us/entra/identity-platform/howto-create-self-signed-certificate

MicrosoftSearch/graph-connector-agent.md

@@ -155,7 +155,7 @@ $fileName = "agentcert" # What do you want to call the cert files? without the f
 $yearsValid = 10 # Number of years until you need to renew the certificate
 $certStoreLocation = "cert:\LocalMachine\My"
 $expirationDate = (Get-Date).AddYears($yearsValid)
-$certificate = New-SelfSignedCertificate -DnsName $dnsName -CertStoreLocation $certStoreLocation -NotAfter $expirationDate -KeyExportPolicy Exportable -KeySpec Signature
+$certificate = New-SelfSignedCertificate -DnsName $dnsName -CertStoreLocation $certStoreLocation -NotAfter $expirationDate -KeyExportPolicy Exportable -KeySpec Signature -KeyLength 2048 -KeyAlgorithm RSA -HashAlgorithm SHA256
 $certificatePath = $certStoreLocation + '\' + $certificate.Thumbprint
 $filePath = $folderPath + '\' + $fileName
 $securePassword = ConvertTo-SecureString -String $password -Force -AsPlainText