clean up non-ASCII comments

Change-Id: I07ad00133f6a938de70a94024a0ebe36c6c542bb
Reviewed-on: https://skia-review.googlesource.com/6524
Commit-Queue: Hal Canary <halcanary@google.com>
Reviewed-by: Hal Canary <halcanary@google.com>
diff --git a/src/effects/SkDisplacementMapEffect.cpp b/src/effects/SkDisplacementMapEffect.cpp
index d9c1079..7d5a79a 100644
--- a/src/effects/SkDisplacementMapEffect.cpp
+++ b/src/effects/SkDisplacementMapEffect.cpp
@@ -571,7 +571,7 @@
     const char* scaleUni = args.fUniformHandler->getUniformCStr(fScaleUni);
     const char* dColor = "dColor";
     const char* cCoords = "cCoords";
-    const char* nearZero = "1e-6"; // Since 6.10352e−5 is the smallest half float, use
+    const char* nearZero = "1e-6"; // Since 6.10352e-5 is the smallest half float, use
                                    // a number smaller than that to approximate 0, but
                                    // leave room for 32-bit float GPU rounding errors.