remove mmap from the default features list

I committed this change accidentally in
a12fa7b8a4131d77c35eda5c680b9307a0fc28d3. Thanks to @ArmoredPony for
catching this in https://github.com/BLAKE3-team/BLAKE3/issues/452.

1 files changed, 1 insertions, 1 deletions

diff --git a/Cargo.toml b/Cargo.toml
index 0f5a861..7bf3c4a 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -10,7 +10,7 @@ readme = "README.md"
 edition = "2021"
 
 [features]
-default = ["std", "mmap"]
+default = ["std"]
 
 # The NEON implementation does not participate in dynamic feature detection,
 # which is currently x86-only. If "neon" is on, NEON support is assumed. Note