docs: fix typos in error messages and Go doc comments

[Avicennasis]

Summary

Fix typos across 6 files:

• auto_cache.go, auto_cache_fake.go: Fix typo in error message — "nof found" → "not found"
• byte_cache_blackhole.go, byte_cache_wrapper.go, struct_cache_dummy.go: Update Go doc comments from "do nothing" to "does nothing" for consistency (matches existing ClearSet comment style in the same files)
• struct_cache_dummy.go: Fix type doc comment — "accept" → "accepts", "return" → "returns"
• metric/metric.go: Fix grammar — "for minimize" → "for minimizing"

No functional changes — comments and error message text only.