.ci/lint.R: fix --help behaviour (#7464)

* .ci/lint.R: fix --help

* Terminate with comma, NULL

---------

Co-authored-by: Michael Chirico <[email protected]>

Author: aitap

.ci/lint.R

@@ -3,10 +3,11 @@
 args = commandArgs(TRUE)
 if (identical(args, '--help')) {
   writeLines(c(
-    'Usage: Rscript .ci/lint.R .ci/linters/<KIND> <WHERE> <WHAT> [PREPROCESS]',
+    'Usage: Rscript .ci/lint.R .ci/linters/<KIND> <WHERE> <WHAT>',
     'KIND must name the directory containing the *.R files defining the linter functions.',
     'WHERE must name the directory containing the files to lint, e.g. "po", or "src".',
     "WHAT must contain the regular expression matching the files to lint, e.g., '[.]po$', or '[.][ch]$'.",
+    NULL
   ))
   q('no')
 }