bwa: fix bug :46

src/nf_modules/bwa/main.nf

@@ -43,7 +43,7 @@ if (file_id.containsKey('library')) {
 bwa_mem_R = "@RG\\tID:${library}\\tSM:${library}\\tLB:lib_${library}\\tPL:illumina"
 """
 bwa mem -t ${task.cpus} \
--R '${params.bwa_mem_R}' \
+-R '${bwa_mem_R}' \
 ${index_id} ${reads[0]} ${reads[1]} 2> \
   ${file_id}_bwa_report.txt | \
   samtools view -@ ${task.cpus} -Sb - > ${file_id}.bam