pagectl: skip metadata file in pagectl draw-timeline (#4872)

## Problem

Running `pagectl draw-timeline` on a pageserver directory wasn't working
out of the box because it trips up on the `metadata` file.

## Summary of changes

Just ignore the `metadata` file in the list of input files passed to
`draw-timeline`.

pageserver/ctl/src/draw_timeline_dir.rs

@@ -23,6 +23,7 @@
 //!      <https://grafana.com/tutorials/build-a-panel-plugin/>
 use anyhow::Result;
 use pageserver::repository::Key;
+use pageserver::METADATA_FILE_NAME;
 use std::cmp::Ordering;
 use std::io::{self, BufRead};
 use std::path::PathBuf;
@@ -71,6 +72,10 @@ pub fn main() -> Result<()> {
         let line = PathBuf::from_str(&line).unwrap();
         let filename = line.file_name().unwrap();
         let filename = filename.to_str().unwrap();
+        if filename == METADATA_FILE_NAME {
+            // Don't try and parse "metadata" like a key-lsn range
+            continue;
+        }
         let range = parse_filename(filename);
         ranges.push(range);
     }