[lldb][test] Fix flaky DIL array subscript test by reducing array indexes (#141738)

This test has been flaky on Linaro's Windows on Arm bot and I was 
able to reproduce it within 10 or so runs locally.

When it fails it's because we failed to read the value of int_arr[100].
When that happens the memory looks like this:
```
[0x0000006bf88fd000-0x0000006bf8900000) rw-      <-- sp (0x0000006bf88ffe20)
[0x0000006bf8900000-0x0000025fec900000) ---      <-- int_arr[100] (0x0000006bf8900070)
```
The first region is the stack and the stack pointer is pointing
within that region, as expected.

The second region is where we are trying to read int_arr[100] from
and this is not mapped because we're trying to read above the start
of the stack.

Sometimes the test passes I think because ASLR / DYNAMICBASE moves
the start of the stack down enough so there is some readable memory
at the top.

https://learn.microsoft.com/en-us/cpp/build/reference/dynamicbase?view=msvc-170

Note "Because ASLR can't be disabled on ARM, ARM64, or ARM64EC
architectures,
/DYNAMICBASE:NO isn't supported for these targets.". Which means on this
bot,
the layout is definitely being randomised.

We don't need to be testing indexes this large. So I've changed the two 
test indexes to 3 (1 beyond the end) and 10 (a larger distance beyond
the end).
We know that index 42 always worked on the bot, so 10 should be fine,
and
did not fail locally.