MongoDB IDX sample doesn't parse at CLI

The sample given for defining an index at the CLI is this document section:

Indexes, you can enter it as a string or as a file, e.g., --idx @indexes-file.json or --idx "[{"key": {"keys": ["_ts"]},"options": {"expireAfterSeconds": 1000}}, {"key": {"keys": ["user_id", "user_address"]}, "options": {"unique": "true"}}]".

doesn't parse at the CLI and the double quotes should be replaced with single quotes:

--idx '[{"key": {"keys": ["_ts"]},"options": {"expireAfterSeconds": 1000}}, {"key": {"keys": ["user_id", "user_address"]}, "options": {"unique": "true"}}]'.

There are also a few other doc pages that use the same example that require an update

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#### Document Details

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* ID: a5323936-60e0-75a1-9f91-ea908249897d
* Version Independent ID: e3c52896-95e5-1fea-fc8a-ab7170e95333
* Content: [az cosmosdb mongodb collection](https://docs.microsoft.com/en-us/cli/azure/cosmosdb/mongodb/collection?view=azure-cli-latest#az-cosmosdb-mongodb-collection-update)
* Content Source: [latest/docs-ref-autogen/cosmosdb/mongodb/collection.yml](https://github.com/MicrosoftDocs/azure-docs-cli/blob/master/latest/docs-ref-autogen/cosmosdb/mongodb/collection.yml)
* Service: **cosmos-db**
* GitHub Login: @rloutlaw
* Microsoft Alias: **routlaw**