keyboard: Switch default maps for surrounding pairs to the delimiters themselves

[pokey]

in this map: https://github.com/cursorless-dev/cursorless/blob/5f94e084af3f67e07a6d6f68e478365e7a691d31/packages/cursorless-vscode/src/keyboard/keyboard-config.fixture.json#L85-L100

we would eg change wb to {