Bump src/deps/Imath from bd254da to 3ffb078 (AcademySoftwareFoundation#1291)

this reduces compiler warnings from Imath almost completely

Bumps [src/deps/Imath](https://github.com/AcademySoftwareFoundation/Imath) from `bd254da` to `3ffb078`.
- [Release notes](https://github.com/AcademySoftwareFoundation/Imath/releases)
- [Commits](AcademySoftwareFoundation/Imath@bd254da...3ffb078)

---
updated-dependencies:
- dependency-name: src/deps/Imath
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Signed-off-by: Michele Spina <[email protected]>

Author: dependabot[bot]