fix(code-snippet): showMoreLess={false} should hide button

[metonym]

Fixes #1536

Currently, the following does not work as intended:

<CodeSnippet type="multi" {code} showMoreLess={false} />

The root cause is that showMoreLess is dynamically computed based on the code snippet height (the button is shown if a multi-line code snippet exceeds 255px). Additionally, the showMoreLess prop is initialized as false when it should be the opposite (allowing the consumer to set it to false).

This PR fixes the logic:

• flip the default boolean value
• only compute the show logic if showMoreLess is not false

Additionally, it adds the following examples to the docs:

• "Hidden show more button"
• "Hidden copy, show more buttons"

[metonym]

Released in v0.82.11.