Fix issue #204: Remove a poorly designed challenge

[Simon-Stone]

Fixes issue #204 by simply removing the challenge in question.

[github-actions[bot]]

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[martinosorb]

Thank you for taking care of this -- I agree that that exercise is poorly designed. However, I'm a bit hesitant on leaving this episode without any exercise. Would it be feasible to modify it so that e.g. it asks a simple question about the scope of variables in a code example like the one there?

[tobyhodges]

How about this?

:::::::::::::::::::::::::::::::::::::::  challenge

## Tracing Global Variables

The code block below is a repeat of the example above, 
but with a global variable called `temperature` defined 
before the `adjust` function definition.

```python
pressure = 103.9 
temperature = 294.15 # checkpoint 1

def adjust(t):
    temperature = t * 1.43 / pressure
    return temperature # checkpoint 2

print('adjusted:', adjust(0.9))
print('temperature after call:', temperature) # checkpoint 3

1. Think through the code block line-by-line, tracing the value of the variables as the program is run. Fill in the table with the values of variables called pressure, temperature, and t at each of the checkpoints (marked with comments in the code block). Write "undefined" if the value of a variable has not yet been set.

   Checkpoint	pressure	temperature	t
   1
   2
   3

2. Before running this code block, think about what you expect the result to be. Can you identify which of the options below is correct?
   1. A NameError again

   2. adjusted: 0.01238691049085659
      temperature after call: 294.15

   3. adjusted: 0.01238691049085659
      temperature after call: 0.01238691049085659

3. Now run the code. Did you predict the result correctly?

::::::::::::::: solution

After the global variables are first defined, their values are not modified by any of the subsequent lines. No global variable called t is ever created outside the adjust function, so this variable remains undefined at all of the checkpoints:

Checkpoint	pressure	temperature	t
1	103.9	294.15	undefined
2	103.9	294.15	undefined
3	103.9	294.15	undefined

This means that the output produced by the code block is option 2:

adjusted: 0.01238691049085659
temperature after call: 294.15

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