Remove unused dexpreopt install path function

`odexOnSystemOther` (presumably) returns a boolean indicating whether
.odex/.vdex files should be installed in system_other.img. The
installation location logic is now colocated in build/soong/dexpreopt
package, so we can delete this unused function.

Test: go build ./java
Change-Id: Ibd1a3a0b945f8d7953baad05cbaf65cb58b5a05a