docs: Fixing bad summary fragment in Canvas.isOpaque()

The first sentence of the Canvas.isOpaque() comment contained an "i.e.",
which the docs engine interprets as the end of the summary fragment (per
the Javadoc standard). Replaced "i.e." with "that is" to fix this.

Docs-only change, no code affected. NO_TEST , fixes a doc bug.

Change-Id: Ib733365cc8654acdaf1d9b5bc891e0aa67210bf1
Test: [go/abtd docs build]
Fixes: 267544675

graphics/java/android/graphics/Canvas.java

@@ -241,7 +241,7 @@ public class Canvas extends BaseCanvas {
 
     /**
      * Return true if the device that the current layer draws into is opaque
-     * (i.e. does not support per-pixel alpha).
+     * (that is, it does not support per-pixel alpha).
      *
      * @return true if the device that the current layer draws into is opaque
      */