Update utils.go to fix the decoding process of the accessToken

[yuunaka1]

The accessToken (JWS Payload) uses Base64URL encoding, not Base64 encoding. Therefore, the base64.RawURLEncoding function should be used for the decoding.
ref: https://datatracker.ietf.org/doc/html/rfc7515#section-7.1

[github-actions]

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[yuunaka1]

I have read the CLA Document and I hereby sign the CLA

[KinakoExE]

@mvlipka @ddlees
Hello, I encountered an AzureHound bug that throws the error:
illegal base64 data at input byte XXX.
This PR resolves the issue, so I would strongly recommend merging it.

Problem

Entra ID returns URL-safe base64-encoded JWTs. However, AzureHound attempts to decode them using the standard (non–URL-safe) base64 decoder. As a result, even valid access tokens can trigger a fatal error.

Here’s a real example I ran into:

$ ./azurehound list -t "$TENANT_ID" -j "$ACCESS_TOKEN" -o output.json -v 1
...
No configuration file located at /home/kali/.config/azurehound/config.json
2025-08-21T13:15:50+09:00 DBG testing connections
2025-08-21T13:15:50+09:00 DBG testing connections
2025-08-21T13:15:50+09:00 ERR encountered unrecoverable error error="failed to create new Azure client: illegal base64 data at input byte 634"