Oxford comma

Co-authored-by: Tim Gross <tgross@hashicorp.com>

website/content/docs/commands/job/run.mdx

@@ -34,7 +34,7 @@ exit after scheduling and deployment have finished or failed.
 On successful job submission and scheduling, exit code 0 will be returned. If
 there are job placement issues encountered (unsatisfiable constraints, resource
 exhaustion, etc), then the exit code will be 2. Any other errors, including
-deployment failures, client connection issues or internal errors, are indicated
+deployment failures, client connection issues, or internal errors, are indicated
 by exit code 1.
 
 If the job has specified the region, the `-region` flag and `$NOMAD_REGION`