t: fix Lexer line count for $() inside double-quoted strings

scan_dqstring's post-loop newline counter re-counts newlines that were already counted during recursive parsing of $() bodies. This happens because scan_dollar returns text containing newlines (from multi-line command substitutions), and the catch-all counter at the end of scan_dqstring counts all of them again. Fix this by counting newlines inline as non-special characters are consumed, and removing the post-loop catch-all. Each newline is now counted exactly once: literal newlines at the inline match, line splices at the backslash handler, and $() newlines by scan_token during the recursive parse. This is a latent bug: any consumer that relies on token line numbers rather than byte offsets would get incorrect results for tokens following a multi-line $() inside a double-quoted string. chainlint is not affected because it annotates the original body text using byte offsets, not token line numbers. Signed-off-by: Michael Montalbo <mmontalbo@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>