Remove superflous 'with-safe-mode' feature which isn't actually used anywhere

Signed-off-by: Victor Porof <victor.porof@gmail.com>

Cargo.toml

@@ -14,9 +14,8 @@ categories = ["database"]
 exclude = ["/tests/envs/*"]
 
 [features]
-default = ["with-safe-mode"]
+default = []
 backtrace = ["failure/backtrace", "failure/std"]
-with-safe-mode = ["hashbrown/serde", "id-arena", "log", "serde/derive", "serde/rc"]
 with-asan = ["lmdb-rkv/with-asan"]
 with-fuzzer = ["lmdb-rkv/with-fuzzer"]
 with-fuzzer-no-link = ["lmdb-rkv/with-fuzzer-no-link"]
@@ -26,14 +25,14 @@ arrayref = "0.3"
 bincode = "1.0"
 bitflags = "1"
 byteorder = "1"
-hashbrown = { version = "0.6", optional = true }
-id-arena = { version = "2.2", optional = true }
+hashbrown = { version = "0.6", features = ["serde"] }
+id-arena = "2.2"
 lazy_static = "1.0"
 lmdb-rkv = "0.12.3"
-log = { version = "0.4", optional = true }
+log = "0.4"
 ordered-float = "1.0"
 uuid = "0.7"
-serde = "1.0"
+serde = { version = "1.0", features = ["derive", "rc"] }
 serde_derive = "1.0"
 url = "2.0"