lint: Drop check to enforce encoding to be specified in Python scripts

The check was incomplete and brittle. A better check would be to enable
`PYTHONWARNDEFAULTENCODING=1`
https://docs.python.org/3/whatsnew/3.10.html#optional-encodingwarning-and-encoding-locale-option

However, it is unclear what the goal of adding explicit encodings
everywhere is, given that:

* Most modern systems already have UTF-8 enabled by default, except for
  Windows.
* Python 3.15 will likely enable it globally by default, according to
  https://peps.python.org/pep-0686/#abstract
* Adding the explicit encodings will bloat all code for no benefit.

So remove the lint check and drop all redundant encoding= kwargs.

All encoding= that are set for a reason, are kept.

test/lint/lint-python-utf8-encoding.py

@@ -1,73 +0,0 @@
-#!/usr/bin/env python3
-#
-# Copyright (c) 2018-2022 The Bitcoin Core developers
-# Distributed under the MIT software license, see the accompanying
-# file COPYING or http://www.opensource.org/licenses/mit-license.php.
-#
-# Make sure we explicitly open all text files using UTF-8 (or ASCII) encoding to
-# avoid potential issues on the BSDs where the locale is not always set.
-
-import sys
-import re
-
-from subprocess import check_output, CalledProcessError
-
-EXCLUDED_DIRS = ["src/crc32c/", "src/secp256k1/"]
-
-
-def get_exclude_args():
-    return [":(exclude)" + dir for dir in EXCLUDED_DIRS]
-
-
-def check_fileopens():
-    fileopens = list()
-
-    try:
-        fileopens = check_output(["git", "grep", r" open(", "--", "*.py"] + get_exclude_args(), text=True, encoding="utf8").splitlines()
-    except CalledProcessError as e:
-        if e.returncode > 1:
-            raise e
-
-    filtered_fileopens = [fileopen for fileopen in fileopens if not re.search(r"encoding=.(ascii|utf8|utf-8).|open\([^,]*, (\*\*kwargs|['\"][^'\"]*b[^'\"]*['\"])", fileopen)]
-
-    return filtered_fileopens
-
-
-def check_checked_outputs():
-    checked_outputs = list()
-
-    try:
-        checked_outputs = check_output(["git", "grep", "check_output(", "--", "*.py"] + get_exclude_args(), text=True, encoding="utf8").splitlines()
-    except CalledProcessError as e:
-        if e.returncode > 1:
-            raise e
-
-    filtered_checked_outputs = [checked_output for checked_output in checked_outputs if re.search(r"text=True", checked_output) and not re.search(r"encoding=.(ascii|utf8|utf-8).", checked_output)]
-
-    return filtered_checked_outputs
-
-
-def main():
-    exit_code = 0
-
-    nonexplicit_utf8_fileopens = check_fileopens()
-    if nonexplicit_utf8_fileopens:
-        print("Python's open(...) seems to be used to open text files without explicitly specifying encoding='utf8':\n")
-        for fileopen in nonexplicit_utf8_fileopens:
-            print(fileopen)
-        exit_code = 1
-
-    nonexplicit_utf8_checked_outputs = check_checked_outputs()
-    if nonexplicit_utf8_checked_outputs:
-        if nonexplicit_utf8_fileopens:
-            print("\n")
-        print("Python's check_output(...) seems to be used to get program outputs without explicitly specifying encoding='utf8':\n")
-        for checked_output in nonexplicit_utf8_checked_outputs:
-            print(checked_output)
-        exit_code = 1
-
-    sys.exit(exit_code)
-
-
-if __name__ == "__main__":
-    main()