tests: use raw string in test-check-code.t
To avoid a SyntaxWarning on Python 3.8 due to invalid \ escape.
Differential Revision: https://phab.mercurial-scm.org/D5837
# See http://EditorConfig.org for the specification
root = true
[*.py]
indent_size = 4
indent_style = space
trim_trailing_whitespace = true
[*.{c,h}]
indent_size = 8
indent_style = tab
trim_trailing_whitespace = true
[*.t]
indent_size = 2
indent_style = space
trim_trailing_whitespace = false