tools/headerversions.c: fix build without SQLite

[whitslack]

Commit 531845971cf94d8e5c0de67c8531578bc2656353 broke the build without SQLite because this code:

new = tal_fmt(NULL, template,
              IF_SQLITE3(sqlite3_libversion_number()));

preprocesses into:

new = tal_fmt(NULL, template,
              );

which has a syntax error. Fix it by moving the comma into the macro argument.

Fixes: 531845971cf94d8e5c0de67c8531578bc2656353 Changelog-None

[!IMPORTANT] Open for merging new PRs until the next PR freeze date is confirmed!

Checklist

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• [x] The changelog has been updated in the relevant commit(s) according to the guidelines.
• [x] Tests have been added or modified to reflect the changes.
• [x] Documentation has been reviewed and updated as needed.
• [x] Related issues have been listed and linked, including any that this PR closes.