misc: Use python f-strings for string formatting

This patch has been generated by applying flynt to the
gem5 repo (ext has been excluded)

JIRA: https://gem5.atlassian.net/browse/GEM5-831

Change-Id: I0935db6223d5426b99515959bde78e374cbadb04
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/68957
Maintainer: Bobby Bruce <bbruce@ucdavis.edu>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Bobby Bruce <bbruce@ucdavis.edu>

configs/deprecated/example/se.py

@@ -159,8 +159,7 @@ if args.bench:
             multiprocesses.append(workload.makeProcess())
         except:
             print(
-                "Unable to find workload for %s: %s"
-                % (get_runtime_isa().name(), app),
+                f"Unable to find workload for {get_runtime_isa().name()}: {app}",
                 file=sys.stderr,
             )
             sys.exit(1)