fixup! Use only the 21L sequence from references

nextstrain_profiles/nextstrain-gisaid-21L/prefilter.smk

@@ -91,10 +91,8 @@ rule gisaid_21L_aligned:
         r"""
         exec 2> {log:q}
 
-        echo "21L" > reference_ids.txt
-
         < {input.references:q} \
-          seqkit grep --by-name -f reference_ids.txt \
+          seqkit grep --by-name --pattern 21L \
         | zstd \
         > {output.aligned}
 
@@ -103,6 +101,4 @@ rule gisaid_21L_aligned:
         | seqkit grep --by-name -f {input.strains:q} \
         | zstd -T$(({threads} - 2)) \
         >> {output.aligned:q}
-
-        rm reference_ids.txt
         """