Fix setting env problem
@ -97,7 +97,7 @@ PS> $Env:CASE_INSENSITIVE=1; cargo run to poem.txt
这回应该得到包含可能有大写字母的 “to” 的行:
```console
$ CASE_INSENSITIVE=1 cargo run to poem.txt
$ (CASE_INSENSITIVE=1; cargo run to poem.txt)
Finished dev [unoptimized + debuginfo] target(s) in 0.0s
Running `target/debug/minigrep to poem.txt`
Are you nobody, too?