ingest/nextclade: Use all available workflow cores

Chatter on Slack regarding workflow runtimes made me realize that since
we only run a single Nextclade job now, we no longer need to put a hard
limit on the threads.

<https://bedfordlab.slack.com/archives/C01LCTT7JNN/p1729629899871479?thread_ts=1729629155.721859&cid=C01LCTT7JNN>

ingest/rules/nextclade.smk

@@ -30,7 +30,7 @@ rule run_nextclade:
         # The lambda is used to deactivate automatic wildcard expansion.
         # https://github.com/snakemake/snakemake/blob/384d0066c512b0429719085f2cf886fdb97fd80a/snakemake/rules.py#L997-L1000
         translations=lambda w: "results/translations/{cds}.fasta",
-    threads: 4
+    threads: workflow.cores
     log:
         "logs/run_nextclade.txt",
     benchmark: