bump MSRV to 1.70

Author: jeromefroe

.github/workflows/main.yml

@@ -16,7 +16,7 @@ jobs:
           - stable
           - beta
           - nightly
-          - 1.65.0  # MSRV
+          - 1.70.0  # MSRV
 
     steps:
       - uses: actions/checkout@v2

README.md

@@ -12,7 +12,7 @@ An implementation of a LRU cache. The cache supports `put`, `get`, `get_mut` and
 all of which are O(1). This crate was heavily influenced by the [LRU Cache implementation in an
 earlier version of Rust's std::collections crate].
 
-The MSRV for this crate is 1.65.0.
+The MSRV for this crate is 1.70.0.
 
 ## Example