Logs: Incorrect block progress calculation

[RuslanProgrammer]

electrs/src/daemon.rs

Lines 784 to 789 in 335b567

	info!(
	"downloaded {}/{} block headers ({:.0}%)",
	result.len(),
	tip_height,
	result.len() as f32 / tip_height as f32 * 100.0
	);

When running regtest, I found the following log:
INFO downloaded 2/1 block headers (200%)

Flow example:
The node has 2 blocks:

• Genesis block at height 0
• One mined block at height 1

So there are 2 headers in total.

Expected behaviour:
Have a log like:
INFO downloaded 2/2 block headers (100%)