Update nextflow compatible version

workflow/nextflow.config

@@ -34,5 +34,5 @@ manifest {
   homePage = 'https://git.biohpc.swmed.edu/BICF/Astrocyte/chipseq_analysis'
   version = '1.1.3'
   mainScript = 'main.nf'
-  nextflowVersion = '>=21.04.1'
+  nextflowVersion = '>=20.01.0'
 }