Previously, due to a bug a `Context` with `isStatement: false` could be
returned in places where a `Context` with `isStatement: true` was
requested. As a result, some statements would be unnecessarily wrapped
in parenthesis.
This commit fixes the bug in `Context#withStatementMode` to always
return a `Context` with the correct `isStatement` value. Note that this
does not have any impact on the generated code other than avoiding some
superfluous parenthesis on certain statements.
PR Close#33514