contrib: Use text=True in subprocess over manual encoding handling

All touched Python scripts already assume and require UTF8, so manually
specifying encoding or decoding for functions in the subprocess module
is redundant to just using text=True, which exists since Python 3.7

test/lint/lint-files.py

@@ -76,7 +76,7 @@ def get_git_file_metadata() -> dict[str, FileMeta]:
     '''
     Return a dictionary mapping the name of all files in the repository to git tree metadata.
     '''
-    files_raw = check_output(CMD_ALL_FILES).decode("utf8").rstrip("\0").split("\0")
+    files_raw = check_output(CMD_ALL_FILES, text=True).rstrip("\0").split("\0")
     files = {}
     for file_spec in files_raw:
         meta = FileMeta(file_spec)
@@ -169,7 +169,7 @@ def check_shebang_file_permissions(files_meta) -> int:
     """
     Checks every file that contains a shebang line to ensure it has an executable permission
     """
-    filenames = check_output(CMD_SHEBANG_FILES).decode("utf8").strip().split("\n")
+    filenames = check_output(CMD_SHEBANG_FILES, text=True).strip().split("\n")
 
     # The git grep command we use returns files which contain a shebang on any line within the file
     # so we need to filter the list to only files with the shebang on the first line
@@ -198,7 +198,7 @@ def check_shebang_file_permissions(files_meta) -> int:
 
 
 def main() -> NoReturn:
-    root_dir = check_output(CMD_TOP_LEVEL).decode("utf8").strip()
+    root_dir = check_output(CMD_TOP_LEVEL, text=True).strip()
     os.chdir(root_dir)
 
     files = get_git_file_metadata()