Fix for Extra Parenthesis in pgbench progress message

Hi,

I noticed an issue in the pgbench progress message where an extra
closing parenthesis )) appears, as shown below:

7000000 of 10000000 tuples (70%) of pgbench_accounts done (elapsed 19.75
s, remaining 8.46 s))

This occurs when running commands like pgbench -i -s100 and is caused by
leftover characters when using \r with fprintf. I made a patch to
address this by adding extra spaces before \r, which clears any
remaining characters. While effective, I recognize this solution may not
be the most sophisticated.

A more refined solution, such as using string padding, might be ideal
for cases like this.

Best,
Yushi Ogiwara