Remove giant string from bottom of vumi.utils.

It looks like:

```python
### SAMPLE CONFIG PARAMETERS - REPLACE 'x's IN OPERATOR_NUMBER

"""
COUNTRY_CODE: "27"

OPERATOR_NUMBER:
    VODACOM: "2782xxxxxxxxxxx"
    MTN: "2783xxxxxxxxxxx"
    CELLC: "2784xxxxxxxxxxx"
    VIRGIN: ""
    8TA: ""
    UNKNOWN: ""

OPERATOR_PREFIX:
    2771:
        27710: MTN
        27711: VODACOM
        27712: VODACOM
        27713: VODACOM
        27714: VODACOM
        27715: VODACOM
        27716: VODACOM
        27717: MTN
        27719: MTN

    2772: VODACOM
    2773: MTN
    2774:
        27740: CELLC
        27741: VIRGIN
        27742: CELLC
        27743: CELLC
        27744: CELLC
        27745: CELLC
        27746: CELLC
        27747: CELLC
        27748: CELLC
        27749: CELLC

    2776: VODACOM
    2778: MTN
    2779: VODACOM
    2781:
        27811: 8TA
        27812: 8TA
        27813: 8TA
        27814: 8TA

    2782: VODACOM
    2783: MTN
    2784: CELLC

"""
```