/usr/share/lintian/overrides/btrfs-tools is in btrfs-tools 3.12-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 | # To avoid micro-packaging, btrfs-tools does contain its library in the same
# package, therefore overwriting the following two lintian warnings.
btrfs-tools: non-dev-pkg-with-shlib-symlink
btrfs-tools: package-name-doesnt-match-sonames
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