Update Rust crate num_cpus to 1.15.0

Author: renovate[bot]

Cargo.toml

@@ -23,7 +23,7 @@ git-cvs-fast-import-process = { path = "internal/process" }
 git-cvs-fast-import-state = { path = "internal/state" }
 git-fast-import = { path = "git-fast-import" }
 log = "0.4.14"
-num_cpus = "1.13.1"
+num_cpus = "1.15.0"
 parse_duration = "2.1.1"
 patchset = { path = "patchset" }
 rcs-ed = { path = "rcs-ed" }