Inconsistency in the binary values of supported environment variables for benchmarks

[gojakuch]

Currently, in the BENCHMARKING.md file, there are these variables specified:

...
* `DETAILED={0,1}` - selects whether detailed benchmarks should be run. This
    generally provides extra, verbose information at the cost of one or more
    extra benchmark runs. It can be either `0` (off) or `1` (on).
* `GPU_TIMER={true, false}` - If set to `true`, use the gpu timer, which is
    valid for cuda/hip executor, to measure the timing. Default is `false`.
...

{0, 1} and {true, false} as possibilities for different variables seem to be an unnecessary inconsistency to me.