-record flag example

Hi I was trying to record the output for a test and I got the following

```
$ go test -run TestDictWordList -record
Foo {} no recording exists with this name: TestDictWordList/Foo

PASS
```

I also tried with a double dash between
```
$ go test -run TestDictWordList -- -record
Foo {} no recording exists with this name: TestDictWordList/Foo

PASS
```

The only way I could get it to work was

```
COPYIST_RECORD=1 go test -run TestDictWordList
```

FTR
```
$ go version
go version go1.17.5 darwin/arm64
```

go.mod has
```
github.com/cockroachdb/copyist v1.4.1
```

Start with the TestDictWordList test and compare the documented -record command with the working COPYIST_RECORD=1 invocation. Trace how recording options are handled during go test execution, then verify that the command-line example records the test without requiring the environment variable.

Written by the indexing model from the issue text.