fix: include -f option on curl download

[daniel-mohedano]

What does this PR do?

• Add -f option on curl downloads to surface request errors (instead of failing during sha256 check with the errored HTML document).

Motivation

Additional Notes

Now the request failures bubble up instead of being swallowed:

DD_CIVISIBILITY_ENABLED=true
DD_CIVISIBILITY_AGENTLESS_ENABLED=true
DD_ENV=ci
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
curl: (22) The requested URL returned error: 404

While previously the error would look like:

DD_CIVISIBILITY_ENABLED=true
DD_CIVISIBILITY_AGENTLESS_ENABLED=true
DD_ENV=ci
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100     9    0     9    0     0  10368      0 --:--:-- --:--:-- --:--:--  9000
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100     9    0     9    0     0  11042      0 --:--:-- --:--:-- --:--:--  9000
sha256sum: 'standard input': no properly formatted checksum lines found

Possible Drawbacks / Trade-offs

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