Adjust snippet clipping in S3 Glacier example

[camerondurham]

Issue #, if available:
No open issues found.

Description of changes:

Dedent the code snippet to avoid clipping in Glacier example:

Matching closest file that includes full file as snippet rather than pieces: https://github.com/awsdocs/aws-go-developer-guide/blob/master/doc_source/kms-example-create-key.rst

From briefly looking over all snippets in the doc, I believe this is the only full file snippet with this issue. However, there are other clipping errors such as in this file where the import section is clipped and func is missing on CloudWatch Disable Actions On An Alarm.

I have run python build_docs.py singlehtml but unable to completely verify changes locally since the output looked significantly different than current docs. I opted to make a smaller change that exactly matched similar files. I can file an issue with how the doc build failed if desired but all snippets were all off by ~15 lines after the script successfully ran (with warnings).

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Thanks for considering this change! I'm not sure if this repository or SDK is still active but do plan to test and use this. README seems to suggest this repo is still used.

[Paul-B-AWS]

@camerondurham, thanks for raising this issue and also for the pointers to other possible anomalies.

[Paul-B-AWS]

@camerondurham Regarding your comment about the Python build looking significantly different from the web site...
This is a known issue. It stems from metadata that has been added to the code examples that live in the AWS Code Examples Repository.

For example, look at the first 11 lines of create_vault.go.
For the web build, those lines are read and then removed before the code is fed into the build process.
We account for this behavior when calculating the desired line numbers for the content source files.
For example, notice in using-glacier-with-go-sdk.rst (the section for "Create a vault"), we have :lines: 15-.
So for the web build, the code is actually pulled from line (15 + 11 = 26) of the original code example file from the AWS Code Examples Repository.

The local build, on the other hand, doesn't account for the web-build behavior, so starts counting code lines from the beginning of the original code example file.

Hope this explanation helps.

[camerondurham]

@Paul-B-AWS Thank you for the really thorough explanation! That complexity of doc-building is new to me and the details will be helpful in case I submit another PR for this.