Bump MSRV to 1.48

async-lock 2.7.0 requires Rust 1.48.

```
error[E0658]: use of unstable library feature 'future_readiness_fns'
   --> /home/runner/.cargo/registry/src/github.com-1ecc6299db9ec823/async-lock-2.7.0/src/once_cell.rs:430:45
    |
430 |             self.initialize_or_wait(move || std::future::ready(closure()), &mut Blocking),
    |                                             ^^^^^^^^^^^^^^^^^^
    |
```

.github/workflows/ci.yml

@@ -1,5 +1,8 @@
 name: CI
 
+permissions:
+  contents: read
+
 on:
   pull_request:
   push:
@@ -10,6 +13,7 @@ on:
 
 env:
   CARGO_INCREMENTAL: 0
+  CARGO_NET_GIT_FETCH_WITH_CLI: true
   CARGO_NET_RETRY: 10
   CARGO_TERM_COLOR: always
   RUST_BACKTRACE: 1
@@ -47,7 +51,7 @@ jobs:
         os: [ubuntu-latest, windows-latest]
         # When updating this, the reminder to update the minimum supported
         # Rust version in Cargo.toml.
-        rust: ['1.47']
+        rust: ['1.48']
     steps:
       - uses: actions/checkout@v3
       - name: Install Rust

.github/workflows/release.yml

@@ -1,5 +1,8 @@
 name: Release
 
+permissions:
+  contents: write
+
 on:
   push:
     tags:

Cargo.toml

@@ -6,7 +6,7 @@ name = "async-net"
 version = "1.7.0"
 authors = ["Stjepan Glavina <stjepang@gmail.com>"]
 edition = "2018"
-rust-version = "1.47"
+rust-version = "1.48"
 description = "Async networking primitives for TCP/UDP/Unix communication"
 license = "Apache-2.0 OR MIT"
 repository = "https://github.com/smol-rs/async-net"