Update MSRV for no default features

Author: gyscos

Cargo.toml

@@ -11,7 +11,7 @@ version = "0.12.1+zstd.1.5.2"
 exclude = ["assets/*.zst"]
 readme = "Readme.md"
 edition = "2018"
-rust-version = "1.51"
+rust-version = "1.43"  # Some features (including default ones) can raise this value
 
 [package.metadata.docs.rs]
 features = ["experimental", "zstdmt", "zdict_builder", "doc-cfg"]

zstd-safe/Cargo.toml

@@ -10,7 +10,7 @@ repository = "https://github.com/gyscos/zstd-rs"
 license = "MIT/Apache-2.0"
 readme = "Readme.md"
 edition = "2018"
-rust-version = "1.51" # With the bindgen feature, this jumps to 1.53
+rust-version = "1.43" # This can be higher depending on the features (including default features)
 
 [package.metadata.docs.rs]
 features = ["experimental", "arrays", "std", "zdict_builder", "doc-cfg"]