Revert "fix: remove trailing null characters from decoded string in StringRegField"

This reverts commit df1852d.

It seems leaving the traling null characters is intentional.

Author: ishidawataru

sonic_platform_base/sonic_xcvr/fields/xcvr_field.py

@@ -221,7 +221,7 @@ def __init__(self, name, offset, *fields, **kwargs):
         self.format = kwargs.get("format", ">%ds" % self.size)
 
     def decode(self, raw_data, **decoded_deps):
-        return struct.unpack(self.format, raw_data)[0].decode(self.encoding, 'ignore').rstrip("\x00")
+        return struct.unpack(self.format, raw_data)[0].decode(self.encoding, 'ignore')
 
 class CodeRegField(RegField):
     """