Rename EncoderBench.cpp to EncodeBench.cpp

Dropping the "r" makes it consistent with both the class name and
Benchmark::getName.

Bug: skia:
Change-Id: I17bcf699d162c678daabf92b4e39b7230428b98b
Reviewed-on: https://skia-review.googlesource.com/c/163280
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>

gn/bench.gni

@@ -44,7 +44,7 @@ bench_sources = [
   "$_bench/DisplacementBench.cpp",
   "$_bench/DrawBitmapAABench.cpp",
   "$_bench/DrawLatticeBench.cpp",
-  "$_bench/EncoderBench.cpp",
+  "$_bench/EncodeBench.cpp",
   "$_bench/FontCacheBench.cpp",
   "$_bench/FontScalerBench.cpp",
   "$_bench/FSRectBench.cpp",