Revert "[MLIR] Add IndexAttr to primitive attributes kinds in tablegen."

This reverts commit 997f33cf. Breaks check-mlir

******************** TEST 'MLIR :: IR/attribute.mlir' FAILED ********************
Script:
--
: 'RUN: at line 1';   mlir-opt llvm-project/mlir/test/IR/attribute.mlir -split-input-file -verify-diagnostics | /FileCheck llvm-project/mlir/test/IR/attribute.mlir
--
Exit Code: 1

Command Output (stderr):
--
llvm-project/mlir/test/IR/attribute.mlir split at line #1:19:3: error: unexpected error: 'test.int_attrs' op requires attribute 'index_attr'
  "test.int_attrs"() {
  ^
llvm-project/mlir/test/IR/attribute.mlir split at line #120:6:3: error: unexpected error: 'test.int_attrs' op requires attribute 'index_attr'
  "test.int_attrs"() {
  ^
llvm-project/mlir/test/IR/attribute.mlir split at line #120:5:6: error: expected error "'si32_attr' failed to satisfy constraint: 32-bit signed integer attribute" was not produced
  // expected-error @+1 {{'si32_attr' failed to satisfy constraint: 32-bit signed integer attribute}}
     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
llvm-project/mlir/test/IR/attribute.mlir split at line #133:5:3: error: unexpected error: 'test.int_attrs' op requires attribute 'index_attr'
  "test.int_attrs"() {
  ^
llvm-project/mlir/test/IR/attribute.mlir split at line #133:4:6: error: expected error "'ui32_attr' failed to satisfy constraint: 32-bit unsigned integer attribute" was not produced
  // expected-error @+1 {{'ui32_attr' failed to satisfy constraint: 32-bit unsigned integer attribute}}
     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
llvm-project/mlir/test/IR/attribute.mlir:9:12: error: CHECK: expected string not found in input
 // CHECK: any_i32_attr = 5 : ui32
           ^
<stdin>:3:1: note: scanning from here
module {
^
<stdin>:21:28: note: possible intended match here
 "test.non_negative_int_attr"() {i32attr = 5 : i32, i64attr = 10 : i64} : () -> ()