Variable with the same name can't be declared in the local scope if the global one is declared read-only

[林博仁Buo-ren , Lin]

Configuration Information [Automatically generated, do not change]:
Machine: x86_64
OS: linux-gnu
Compiler: gcc
Compilation CFLAGS: -g -O2
-fdebug-prefix-map=/build/bash-a6qmCk/bash-5.0=.
-fstack-protector-strong -Wformat -Werror=format-security -Wall
-Wno-parent
heses -Wno-format-security
uname output: Linux brlin-musicha-mz-530 5.4.0-52-generic #57-Ubuntu
SMP Thu Oct 15 10:57:00 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
Machine Type: x86_64-pc-linux-gnu

Bash Version: 5.0
Patch Level: 17
Release Status: release

Description:
       Example script reproducing the bug:

       ```bash
       #!/usr/bin/env bash
       # Depict the variable shadowing phenomenon
       # ./depict-the-variable-shadowing-phenomenon.bash
       set \
           -o errexit \
           -o errtrace \
           -o nounset

       declare -r variable_shadowed='(Value to be shadowed in the function)'

       check_values_of_variables_in_different_scope(){
           local -r variable_shadowed="Another value"

           printf 'In the %s context: \n' "${FUNCNAME[0]}"
           printf 'variable_shadowed = %s\n' "${variable_shadowed}"
       }
       check_values_of_variables_in_different_scope
       ```

       ## Expected behavior

       ```
       $ ./depict-the-variable-shadowing-phenomenon.bash
       In the check_values_of_variables_in_different_scope context:
       variable_shadowed = Another value
       ```

       ## Current behavior

       ```
       $ LANG=C ./depict-the-variable-shadowing-phenomenon.bash
       ./depict-the-variable-shadowing-phenomenon.bash: line 11:
local: variable_shadowed: readonly variable
       ```

Repeat-By:
       Refer the "Descripton" section.

Fix:
       I suggest that bash shouldn't trigger the error, if the
variable to be set is a `different` variable
       instantiated by the variable shadowing mechanism.