Revert of Implement support for using GL ES 3.0 with command buffer (patchset #6 id:100001 of https://codereview.chromium.org/1684413003/ )

Reason for revert:
The dependency, ES3 implementation in command_buffer_gles2, got reverted.

Original issue's description:
> Implement support for using GL ES 3.0 with command buffer
>
> Adds a new 'api': --config gpu(api=commandbuffer3) for dm/nanobench.
>
> BUG=skia:4943
> GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1684413003
>
> Committed: https://skia.googlesource.com/skia/+/45c2c8166bbd84a87e29fdd344b39e36e8a28a3f

TBR=bsalomon@google.com
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=skia:4943
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1744963002

Review URL: https://codereview.chromium.org/1744963002
diff --git a/tools/flags/SkCommonFlagsConfig.cpp b/tools/flags/SkCommonFlagsConfig.cpp
index c82e8de..e2aa327 100644
--- a/tools/flags/SkCommonFlagsConfig.cpp
+++ b/tools/flags/SkCommonFlagsConfig.cpp
@@ -64,7 +64,6 @@
 #endif
 #if SK_COMMAND_BUFFER
     "\t\tcommandbuffer\t\tUse command buffer.\n"
-    "\t\tcommandbuffer3\t\tUse command buffer ES 3.0 (experimental).\n"
 #endif
 #if SK_MESA
     "\t\tmesa\t\t\tUse MESA.\n"
@@ -215,11 +214,7 @@
 #endif
 #if SK_COMMAND_BUFFER
     if (value.equals("commandbuffer")) {
-        *outContextType = GrContextFactory::kCommandBufferES2_GLContextType;
-        return true;
-    }
-    if (value.equals("commandbuffer3")) {
-        *outContextType = GrContextFactory::kCommandBufferES3_GLContextType;
+        *outContextType = GrContextFactory::kCommandBuffer_GLContextType;
         return true;
     }
 #endif