Fix some typos

Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed by: George Melikov <mail@gmelikov.ru>
Signed-off-by: John Eismeier <john.eismeier@gmail.com>
Closes #7237

cmd/arcstat/arcstat.py

@@ -280,7 +280,7 @@ def init():
                 "outfile",
                 "help",
                 "verbose",
-                "seperator",
+                "separator",
                 "columns"
             ]
         )
@@ -299,7 +299,7 @@ def init():
             hflag = True
         if opt in ('-v', '--verbose'):
             vflag = True
-        if opt in ('-s', '--seperator'):
+        if opt in ('-s', '--separator'):
             sep = arg
             i += 1
         if opt in ('-f', '--columns'):