reader/spirv: Remove test that only tests SPIR-V val

The error message has recently changed, and is causing rolls to fail.
I don't see any reason why we're testing SPIR-V val here. Just remove the test.

Bug: tint:912
Change-Id: Ia24f81a8cc86edafe893493279f7aaa73f1d746a
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/70666
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: David Neto <dneto@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>

src/reader/spirv/parser_impl_module_var_test.cc

@@ -4698,50 +4698,6 @@ fn main([[location(9)]] x_1_param : f32, [[location(11)]] x_1_param_1 : vec4<f32
   EXPECT_EQ(got, expected) << got;
 }
 
-TEST_F(SpvModuleScopeVarParserTest, FlattenStruct_LocOnStruct) {
-  const std::string assembly = R"(
-    OpCapability Shader
-    OpMemoryModel Logical Simple
-    OpEntryPoint Vertex %main "main" %1 %2 %3
-
-    OpName %strct "Communicators"
-    OpMemberName %strct 0 "alice"
-    OpMemberName %strct 1 "bob"
-
-    OpDecorate %strct Location 9
-    OpDecorate %strct Block
-    OpDecorate %2 BuiltIn Position
-
-    %void = OpTypeVoid
-    %voidfn = OpTypeFunction %void
-    %float = OpTypeFloat 32
-    %v4float = OpTypeVector %float 4
-    %strct = OpTypeStruct %float %v4float
-
-    %11 = OpTypePointer Input %strct
-    %13 = OpTypePointer Output %strct
-
-    %1 = OpVariable %11 Input
-    %3 = OpVariable %13 Output
-
-    %12 = OpTypePointer Output %v4float
-    %2 = OpVariable %12 Output
-
-    %main = OpFunction %void None %voidfn
-    %entry = OpLabel
-    OpReturn
-    OpFunctionEnd
-)";
-  auto p = parser(test::Assemble(assembly));
-
-  // The validator rejects this because Location decorations
-  // can only go on OpVariable or members of a structure type.
-  ASSERT_FALSE(p->Parse()) << p->error() << assembly;
-  EXPECT_THAT(p->error(),
-              HasSubstr("Location decoration can only be applied to a variable "
-                        "or member of a structure type"));
-}
-
 TEST_F(SpvModuleScopeVarParserTest,
        EntryPointWrapping_Interpolation_Flat_Vertex_In) {
   // Flat decorations are dropped for integral