fix unpadded base64 decode for polar_whs_ webhook secrets

Author: isala404

crates/forge-runtime/src/webhook/handler.rs

@@ -368,7 +368,7 @@ fn validate_standard_webhooks(
         .or_else(|| secret.strip_prefix("polar_whs_"))
         .unwrap_or(secret);
 
-    let key_bytes = match general_purpose::STANDARD.decode(b64_key) {
+    let key_bytes = match general_purpose::STANDARD_NO_PAD.decode(b64_key) {
         Ok(b) => b,
         Err(_) => return false,
     };