gstlal-inspiral/bin/gstlal_inspiral_bank_splitter : fix the help docs for --group-by-mu

gstlal-inspiral/bin/gstlal_inspiral_bank_splitter

@@ -137,7 +137,7 @@ def parse_command_line():
 	parser.add_option("--approximant", type = "string", action = "append", help = "Must specify an approximant given as mchirp_min:mchirp_max:string")
 	parser.add_option("--f-low", type = "float", metavar = "frequency", help = "Lower frequency cutoff. Required")
 	parser.add_option("--group-by-chi", type = "int", metavar = "N", default = 1, help = "group templates into N groups of chi - helps with SVD. Default 1")
-	parser.add_option("--group-by-mu", type = "int", metavar = "N", default = 20, help = "group templates into N groups of mu1, the 1PN phase term, to help with SVD. Default 20")
+	parser.add_option("--group-by-mu", type = "int", metavar = "N", default = 20, help = "group templates into N groups of mu2, one of the orthogonalized PN-phase coefficients, to help with SVD. Default 20")
 	parser.add_option("--num-banks", metavar = "str", help = "The number of parallel subbanks per SVD bank. More than 2 sub-banks is not recommended and return an error. Setting --num-banks-force forces the program to run through. can be given as a list like 1,2,3,4 then it will split up the bank into N groups with M banks each. (required)") # FIXME The second half of this help message is incomprehensible
 	parser.add_option("--num-banks-force", action = "store_true", help = "Set if you intentially set --num-banks larger than 2.")
 	options, filenames = parser.parse_args()