progs/perf: fix typo in sconscript
diff --git a/progs/perf/SConscript b/progs/perf/SConscript
index 224928b..84f1669 100644
--- a/progs/perf/SConscript
+++ b/progs/perf/SConscript
@@ -12,7 +12,7 @@
       'drawoverhead',
       'fbobind',
       'fill',
-      "readpixels',
+      'readpixels',
       'swapbuffers',
       'teximage',
       'vbo',