Recently, VSCode has started adding double quotes when auto-completing JSX attribute names. For example, auto-completing className will finish the attribute name, add a pair of double quotes, and move the cursor into the quotes:
I prefer to add the quotes myself so I would like to disable this feature.
VSCode added JSX Attribute Completions in the November, 2021 update. This can be disabled by changing "javascript.preferences.jsxAttributeCompletionStyle" and "typescript.preferences.jsxAttributeCompletionStyle" to "none" in the settings.