Fixes https://github.com/turt2live/matrix-media-repo/issues/195

Bump lodash from 4.17.11 to 4.17.15 in /tests/performance

Bumps [lodash](https://github.com/lodash/lodash) from 4.17.11 to 4.17.15.
- [Release notes](https://github.com/lodash/lodash/releases)
- [Commits](https://github.com/lodash/lodash/compare/4.17.11...4.17.15

)

Signed-off-by: dependabot[bot] <support@github.com>

Might help solve https://github.com/turt2live/matrix-media-repo/issues/186

Fixes https://github.com/turt2live/matrix-media-repo/issues/169

Fixes https://github.com/turt2live/matrix-media-repo/issues/185

Fix for https://github.com/turt2live/matrix-media-repo/issues/179 (maybe)

Fixes https://github.com/turt2live/matrix-media-repo/issues/178

Fixes https://github.com/turt2live/matrix-media-repo/issues/176
Fixes https://github.com/turt2live/matrix-media-repo/issues/174

Fixes https://github.com/turt2live/matrix-media-repo/issues/170

3% corruption rate

Untested: whether the thumbnails come out okay when using a shared reader.