Fix missed case for replacing samplerExternalOES strings am: 1736cdf43c am: 119cb3376e am: 43539203d1

Original change: https://android-review.googlesource.com/c/device/generic/goldfish-opengl/+/1707469

Change-Id: I33a1a22d526efc3779aa9ef19352ab13c543aa9e