Restructuring of the file 'Modifying the YAML files' (opensearch-proj…

…ect#8126)

* moved the sections of 'yaml.md' to reflect how they show up in the file system for ease of reading and use
Signed-off-by: [email protected] <[email protected]>

Signed-off-by: [email protected] <[email protected]>

* Update _security/configuration/yaml.md

Signed-off-by: Melissa Vagi <[email protected]>

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Signed-off-by: [email protected] <[email protected]>
Signed-off-by: Melissa Vagi <[email protected]>
Co-authored-by: Melissa Vagi <[email protected]>
Signed-off-by: Eric Pugh <[email protected]>