Bump libm from 0.2.13 to 0.2.15

Bumps [libm](https://github.com/rust-lang/compiler-builtins) from 0.2.13 to 0.2.15.
- [Release notes](https://github.com/rust-lang/compiler-builtins/releases)
- [Changelog](https://github.com/rust-lang/compiler-builtins/blob/master/.release-plz.toml)
- [Commits](rust-lang/compiler-builtins@libm-v0.2.13...libm-v0.2.15)

---
updated-dependencies:
- dependency-name: libm
  dependency-version: 0.2.15
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

Cargo.lock

@@ -26,7 +26,7 @@ conv = "0.3.3"
 embed-doc-image = { version = "0.1.4", optional = true }
 enum_dispatch = "0.3.12"
 itertools = "0.14"
-libm = "0.2.13" # erf
+libm = "0.2.15" # erf
 ndarray = "0.16.1"
 num-traits = "0.2.14"
 png = { version = "0.17.16", optional = true }