Remove AfdoAdditionalProfileDirs product variable

AfdoAdditionalProfileDirs is unconnected to build/make/core/soong_config.mk and is currently unused. Removing AfdoAdditionalProfileDirs will cut down on complexity when we migrate the support of auto-fdo profiles to Bazel cc rules.

b/258684450 proposes an alternative to support the use cases that were meant to be supported by AfdoAdditionalProfileDirs.

Test: existing go tests
Bug: 253540178
Change-Id: I024e48598a560717a1d6c19b16bde3fe65ff1961