Fix mint MDX parse error in OpenAIGPTImageNodeV2

[lin-bot23]

Problem: mint broken-links check fails on built-in-nodes/OpenAIGPTImageNodeV2.mdx because the <= sign in the text is interpreted as MDX syntax by the parser.

Error from CI:

erro Syntax error - Unable to parse built-in-nodes/OpenAIGPTImageNodeV2.mdx -
    32:151: Unexpected character `=` (U+003D) before name, expected a character that can start a name, such as a letter, `$`, or `_`

Fix: Replaced <= 3840 with less than or equal to 3840 to avoid MDX parse conflict.

This is a pre-existing issue on main that breaks the mint-checks CI for any PR, including #1063.

[lin-bot23]

Commenting instead — this fix needs to be merged to main first before #1063's CI can pass, but I don't have merge permissions. @maintainer please merge this fix (or re-run #1063 CI after it's merged).