style(tar): comment spelling fix

Author: scop

completions/tar

@@ -31,7 +31,7 @@
 # FIXME: timeout on tarball listing
 # FIXME: cache 'tar --help' parsing results into global variables
 # FIXME: at least 'tar -<tab>' should show some helping text (apart from just
-#        pure option advices)
+#        pure option advice)
 # FIXME: short option completion should be more intuitive
 #        - verbose mode option should be advised multiple times
 #        - mode option should be advised only once