Berry fix index accessor for rean only bytes

[s-hadinger]

Description:

Berry index accessor b[i] for bytes object would wrongly be not be allowed for read-only bytes() objects (solidified).

Checklist:

• The pull request is done against the latest development branch
• Only relevant files were touched
• Only one feature/fix was added per PR and the code change compiles without warnings
• The code change is tested and works with Tasmota core ESP8266 V.2.7.7
• The code change is tested and works with Tasmota core ESP32 V.3.0.5
• I accept the CLA.

NOTE: The code change must pass CI tests. Your PR cannot be merged unless tests pass