[BOLT] Remove workaround for flushPendingLabels

The code emits an empty MCDataFragment to ensure that the labels are
attached to `SplitSection`. The workaround, due to the removed
`flushPendingLabels` mechanism (see
7500646), is now unneeded.

Pull Request: #97632

Author: MaskRay

bolt/lib/Core/BinaryContext.cpp

@@ -2403,16 +2403,8 @@ BinaryContext::calculateEmittedSize(BinaryFunction &BF, bool FixBranches) {
     Streamer->emitLabel(SplitStartLabel);
     emitFunctionBody(*Streamer, BF, FF, /*EmitCodeOnly=*/true);
     Streamer->emitLabel(SplitEndLabel);
-    // To avoid calling MCObjectStreamer::flushPendingLabels() which is
-    // private
-    Streamer->emitBytes(StringRef(""));
-    Streamer->switchSection(Section);
   }
 
-  // To avoid calling MCObjectStreamer::flushPendingLabels() which is private or
-  // MCStreamer::Finish(), which does more than we want
-  Streamer->emitBytes(StringRef(""));
-
   MCAssembler &Assembler =
       static_cast<MCObjectStreamer *>(Streamer.get())->getAssembler();
   Assembler.layout();