main/ca-certificates: Remove execve call to run-parts in old path

MR !7759 (closed) changed the path of the run-parts binary from the run-parts package to be /bin, the same as the binary from the Busybox package.

The update-ca-certificates binary is supposed to contain 2 execve calls to both /usr/bin/run-parts and /bin/run-parts, in that order. However running a "strings" on the current update-ca-certificates binary only shows it containing a reference to /usr/bin/run-parts - therefore let's remove the execve for the /usr/bin/ path, leaving only the execve for the /bin/ path.