rm_templates: T8609: route_maps.py: split overlong getval to satisfy E501

Line 517 was 161 chars (set_extcommunity_bandwidth_non_transitive parser) and tripped pycodestyle's E501 sanity test in CI. Split the regex source across two lines at the \d+) boundary; under re.VERBOSE the literal newline and indent between regex tokens are stripped at compile time, so the engine sees the same pattern. \s*$ stays on the same line as the closing capture group, so the group-quantifier shape this PR fixes elsewhere isn't reintroduced.