[gimp] devel-docs: use actual em-dashes in performance-logs documentation

[Ell <ell src gnome org>]

commit 0fae46133c5ebe724d2e7ba3698445a40d6b6b33
Author: Ell <ell_se yahoo com>
Date:   Thu Jul 30 18:26:52 2020 +0300

    devel-docs: use actual em-dashes in performance-logs documentation

 devel-docs/performance-logs/performance-logs.md | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)
---
diff --git a/devel-docs/performance-logs/performance-logs.md b/devel-docs/performance-logs/performance-logs.md
index b0876d0ee2..99e0e59dce 100644
--- a/devel-docs/performance-logs/performance-logs.md
+++ b/devel-docs/performance-logs/performance-logs.md
@@ -124,9 +124,9 @@ otherwise.
 
     GIMP normally defers certain information to the end of the log, in order to
     minimize the cost of recording.
-    If the log can't be cleanly finished -- for example, if GIMP crashes or
-    freezes while recording the log -- this information will be missing,
-    rendering the log of limited use.
+    If the log can't be cleanly finished—for example, if GIMP crashes or
+    freezes while recording the log—this information will be missing, rendering
+    the log of limited use.
     In situations like these, a progressive log should be recorded; progressive
     logs include all relevant information at each sample, allowing them to be
     terminated at any time.