fix: yarn classic was adding an invalid @ to the version (#146)

## Description

**Related issue (if any):** fixes #145 

## Checklist

- [x] I have followed this repository's contributing guidelines.
- [x] I will adhere to the project's code of conduct.

Signed-off-by: Ruben Romero Montes <rromerom@redhat.com>

Author: ruromero

src/main/java/com/redhat/exhort/providers/YarnClassicProcessor.java

@@ -138,7 +138,7 @@ private static class NodeMetaData {
       this.nodeName = node.get("name").asText();
       var versionIdx = nodeName.lastIndexOf("@");
       this.name = nodeName.substring(0, versionIdx);
-      this.version = nodeName.substring(versionIdx);
+      this.version = nodeName.substring(versionIdx + 1);
       this.purl = JavaScriptProvider.toPurl(name, version);
       var shadowNode = node.get("shadow");
       this.shadow = shadowNode != null && shadowNode.asBoolean();