Revert "feat: add SQLite storage backend for multi-process optimization"

This reverts commit ed80c59795.

# Conflicts:
#	src/lib.rs
#	src/storage/sqlite.rs

src/study.rs

@@ -2469,34 +2469,6 @@ where
     }
 }
 
-#[cfg(feature = "sqlite")]
-impl<V> Study<V>
-where
-    V: PartialOrd + Send + Sync + serde::Serialize + serde::de::DeserializeOwned + 'static,
-{
-    /// Creates a study backed by a `SQLite` database.
-    ///
-    /// Any existing trials in the database are loaded into memory and
-    /// the trial ID counter is set to one past the highest stored ID.
-    /// New trials are written through to the database on completion.
-    ///
-    /// Uses WAL mode for concurrent readers, making it suitable for
-    /// single-machine multi-process optimization.
-    ///
-    /// # Errors
-    ///
-    /// Returns a [`Storage`](crate::Error::Storage) error if the
-    /// database cannot be opened.
-    pub fn with_sqlite(
-        direction: Direction,
-        sampler: impl Sampler + 'static,
-        path: impl AsRef<std::path::Path>,
-    ) -> crate::Result<Self> {
-        let storage = crate::storage::SqliteStorage::<V>::new(path)?;
-        Ok(Self::with_sampler_and_storage(direction, sampler, storage))
-    }
-}
-
 impl Study<f64> {
     /// Generates an HTML report with interactive Plotly.js charts.
     ///