chore: update docs

[mnagaa]

Summary

In this PR, I want to fix the styles of the terraform snowflake provider documentation to be the same format. There are some expression of the variables in the example (like below) and it is not suitable for the official documentation.

This PR only includes updates for modules that grant privileges:

• use UPPERCASE for granting privilege (privilege = "select" => privilege = "SELECT")
• do not use abbr like database_name = "db" => database_name = "database" and warehouse_name = "wh" => warehouse_name = "warehouse" because some other examples already use "database" for their definitions.

Furthermore, changing the definitions with double quotations seems better as follows.
before

resource snowflake_warehouse_grant grant {
  warehouse_name = "wh"
  privilege      = "MODIFY"

  roles = [
    "role1",
  ]

  with_grant_option = false
}

after

resource "snowflake_warehouse_grant" "grant" {
  warehouse_name = "warehouse"
  privilege      = "MODIFY"

  roles = ["role1", "role2"]

  with_grant_option = false
}

[mnagaa]

@sfc-gh-swinkler Could you please review this change?

[sfc-gh-swinkler]

@mnagaa this looks good, thank you for your contribution!