Fix mixup where SamplePathOverstroke wasn't added

- My sampleapp for the stroking bugs was inflight or something when
this change got made, so it didn't get added to this file.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2076283002

Review-Url: https://codereview.chromium.org/2076283002

gyp/samples.gypi

@@ -78,6 +78,7 @@
     '../samplecode/SamplePathClip.cpp',
     '../samplecode/SamplePathFuzz.cpp',
     '../samplecode/SamplePathEffects.cpp',
+    '../samplecode/SamplePathOverstroke.cpp',
     '../samplecode/SamplePictFile.cpp',
     '../samplecode/SamplePoints.cpp',
     '../samplecode/SamplePolyToPoly.cpp',