free -> reset

The C++ standard library uses ".reset()" where we sometimes write ".free()".
We also use ".reset()" quite a lot.  This standardizes on ".reset()".

This is one more step towards dropping SkAutoTDelete in favor of the standard
std::unique_ptr.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1811723002

Committed: https://skia.googlesource.com/skia/+/0e3738db89e86035ed5d4f629bf58b817b1e5274

Review URL: https://codereview.chromium.org/1811723002
diff --git a/src/pdf/SkPDFDevice.cpp b/src/pdf/SkPDFDevice.cpp
index 3febc1a..6e0dd4b 100644
--- a/src/pdf/SkPDFDevice.cpp
+++ b/src/pdf/SkPDFDevice.cpp
@@ -732,9 +732,9 @@
 }
 
 void SkPDFDevice::init() {
-    fContentEntries.free();
+    fContentEntries.reset();
     fLastContentEntry = nullptr;
-    fMarginContentEntries.free();
+    fMarginContentEntries.reset();
     fLastMarginContentEntry = nullptr;
     fDrawingArea = kContent_DrawingArea;
     if (fFontGlyphUsage.get() == nullptr) {