Fix encoding of decoded/json data in update_{record_binary}_decoded

The patch introducing the is_hexstr type into the argparser was
accidentially also introduce in two locations where we actually don't
expect a hex-string.

This is a partial revert of I6426ea864bec82be60554dd125961a48d7751904

Change-Id: I3c3d2a2753aa7a2566a3b1add7ba70c86499d293
Closes: #6331
diff --git a/pySim/filesystem.py b/pySim/filesystem.py
index 5d1970a..2bc5f01 100644
--- a/pySim/filesystem.py
+++ b/pySim/filesystem.py
@@ -622,7 +622,7 @@
                 self._cmd.poutput(data)
 
         upd_bin_dec_parser = argparse.ArgumentParser()
-        upd_bin_dec_parser.add_argument('data', type=is_hexstr, help='Abstract data (JSON format) to write')
+        upd_bin_dec_parser.add_argument('data', help='Abstract data (JSON format) to write')
         upd_bin_dec_parser.add_argument('--json-path', type=str,
                                         help='JSON path to modify specific element of file only')
 
@@ -882,7 +882,7 @@
         upd_rec_dec_parser = argparse.ArgumentParser()
         upd_rec_dec_parser.add_argument(
             'record_nr', type=int, help='Number of record to be read')
-        upd_rec_dec_parser.add_argument('data', type=is_hexstr, help='Abstract data (JSON format) to write')
+        upd_rec_dec_parser.add_argument('data', help='Abstract data (JSON format) to write')
         upd_rec_dec_parser.add_argument('--json-path', type=str,
                                         help='JSON path to modify specific element of record only')