chore: remove clear_layer_data function

`clear_layer_data()` isn't used within rust-fil-proofs. It was also removed
from proofs-api with the merge of
filecoin-project/rust-filecoin-proofs-api#95.

Author: vmx

filecoin-proofs/src/api/mod.rs

@@ -81,19 +81,6 @@ pub fn clear_caches<Tree: MerkleTreeTrait>(
     Ok(())
 }
 
-// TODO vmx 2023-09-26: The `Tree` generic is not needed, it's only there in order to not breaking
-// the public API. Once we break the API, remove that generic.
-// Ensure that any persisted layer data generated from porep are discarded.
-pub fn clear_layer_data<Tree>(cache_dir: &Path) -> Result<()> {
-    info!("clear_layer_data:start");
-
-    let result = stacked::clear_cache_dir(cache_dir);
-
-    info!("clear_layer_data:finish");
-
-    result
-}
-
 // TODO vmx 2023-09-26: The `Tree` generic is not needed, it's only there in order to not breaking
 // the public API. Once we break the API, remove that generic.
 // Ensure that any persisted vanilla proofs generated from synthetic porep are discarded.