chore: update minimal mio requirement to 0.7.11

[taiki-e]

Motivation

Update minimal mio requirement to 0.7.11 includes tokio-rs/mio#1478 (needed for windows) and tokio-rs/mio#1434 (needed for macos).

Caught in #4490 (comment) by using taiki-e/cargo-minimal-versions#4.

info: running `cargo check --all-features` on tokio-stream (1/1)
   Compiling libc v0.2.69
   Compiling log v0.4.8
   Compiling autocfg v1.0.0
   Compiling memchr v2.2.0
    Checking cfg-if v0.1.2
    Checking arc-swap v0.4.0
    Checking pin-project-lite v0.2.5
    Checking once_cell v1.5.2
    Checking bytes v1.0.0
    Checking futures-core v0.3.0
    Checking futures-sink v0.3.0
   Compiling tokio v1.8.0
    Checking signal-hook-registry v1.1.1
    Checking mio v0.7.6
error[E0425]: cannot find value `TCP_KEEPINTVL` in crate `libc`
    --> /Users/taiki/.cargo/registry/src/github.com-1ecc6299db9ec823/mio-0.7.6/src/sys/unix/tcp.rs:334:15
     |
334  |         libc::TCP_KEEPINTVL,
     |               ^^^^^^^^^^^^^ help: a constant with a similar name exists: `TCP_KEEPALIVE`
     |
    ::: /Users/taiki/.cargo/registry/src/github.com-1ecc6299db9ec823/libc-0.2.69/src/unix/bsd/apple/mod.rs:2259:1
     |
2259 | pub const TCP_KEEPALIVE: ::c_int = 0x10;
     | ---------------------------------------- similarly named constant `TCP_KEEPALIVE` defined here

[Darksonn]

Thanks!