Improve navigation icon logic for better readability and efficiency

[nascriptone]

This pull request refactors the navigationIcon logic to improve code readability and efficiency.

Changes Made

• Simplified the conditional logic for setting the navigationIcon.
• Combined nested blocks to reduce redundancy.

Before

navigationIcon = if (isShowingDetailPage) {
    {
        IconButton(onClick = onBackButtonClick) {
            Icon(
                imageVector = Icons.Filled.ArrowBack,
                contentDescription = stringResource(R.string.back_button)
            )
        }
    }
} else {
    { Box {} }
}

After

navigationIcon = {
    if (isShowingDetailPage) {
        IconButton(onClick = onBackButtonClick) {
            Icon(
                imageVector = Icons.Filled.ArrowBack,
                contentDescription = stringResource(R.string.back_button)
            )
        }
    }
}

Benefits

• Readability: The new code is easier to read and understand.
• Efficiency: Reduces unnecessary nested blocks and simplifies the conditional check.

I have tested the changes to ensure the navigation icon behaves as expected. Please let me know if there are any further adjustments needed.

[nascriptone]

@android-dev-lxl, @OwenScott-GDS, @osuleymanova Could you please review the changes and provide any feedback or suggestions? Your input would be greatly appreciated.

Thank you!