Make GLES 1 tests use ANGLE EGL headers.

This will allow us to more easily support a different test target
topology for the standalone test harness that uses an intermediate
source_set. Also it's better in the long run to only have to worry
about one set of EGL headers.

Bug: angleproject:3162
Change-Id: I738dbb68df1abc0c0569748e18d6826914d90a52
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2233399
Reviewed-by: Jonah Ryan-Davis <jonahr@google.com>
Commit-Queue: Jamie Madill <jmadill@chromium.org>

src/tests/BUILD.gn

@@ -403,7 +403,6 @@ if (build_angle_gles1_conform_tests) {
       "$gles1_conform_root/conform/conformshell",
       "$gles1_conform_root/ctk",
       "$gles1_conform_root/fixed",
-      "$gles1_conform_root/include",
       "$gles1_conform_root/platform",
     ]
 
@@ -752,10 +751,7 @@ if (build_angle_gles1_conform_tests) {
       ":angle_gles1_primtest_no_gtest",
     ]
 
-    include_dirs = [
-      ".",
-      "$gles1_conform_root/conform",
-    ]
+    include_dirs = [ "$gles1_conform_root/conform" ]
 
     sources = [
       "gles1_conformance_tests/PrimtestTests.cpp",