Revert "Add an index for Module Metadata record in the bitcode"

This reverts commit a0ca6ae2d3.  Revert at
Mehdi's request as it is breaking bots.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@290686 91177308-0d34-0410-b5e6-96231b3b80d8

test/Bitcode/metadata-function-blocks.ll

@@ -19,9 +19,6 @@
 ; Each node gets a new number.  Bottom-up traversal of nodes.
 !named = !{!6}
 
-; Before the records we emit an offset to the index for the block
-; CHECK-NEXT:   <INDEX_OFFSET
-
 ; CHECK-NEXT:   <NODE op0=1/>
 !4 = !{!"named"}