logging: Fix log formatting with colored output

The log message is already formatted before being passed to the colorer.
To avoid the exception "TypeError: not enough arguments for format
string", we should use the `nofmt_colorer` instead.

This bug occurs only when the formatted string still contains '%'
character. The following snippet can reproduce the bug:

```
from repo_logging import RepoLogger
RepoLogger(__name__).error("%s", "100% failed")
```

Change-Id: I4e3977b3d21aec4e0deb95fc1c6dd1e59272d695
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/432017
Tested-by: Shik Chen <shik@google.com>
Commit-Queue: Shik Chen <shik@google.com>
Reviewed-by: Mike Frysinger <vapier@google.com>

repo_logging.py

@@ -39,8 +39,8 @@ class _LogColoring(Coloring):
 
     def __init__(self, config):
         super().__init__(config, "logs")
-        self.error = self.colorer("error", fg="red")
-        self.warning = self.colorer("warn", fg="yellow")
+        self.error = self.nofmt_colorer("error", fg="red")
+        self.warning = self.nofmt_colorer("warn", fg="yellow")
         self.levelMap = {
             "WARNING": self.warning,
             "ERROR": self.error,