[ctx_prof] Remove Buffer field in PGOCtxProfWriter

Not needed anymore after PR llvm#92983, and moreover, creating the same issue c49bc1a fixed in `BitcodeWriter.cpp`.

Change-Id: I8e2ecce912725d3c8c800fc7746bcb524a2da121

Author: mtrofin

llvm/include/llvm/ProfileData/PGOCtxProfWriter.h

@@ -60,7 +60,6 @@ enum PGOCtxProfileBlockIDs {
 /// example, value profiling would produce a new record with a new record ID,
 /// containing the profiled values (much like the counters)
 class PGOCtxProfileWriter final {
-  SmallVector<char, 1 << 20> Buff;
   BitstreamWriter Writer;
 
   void writeCounters(const ctx_profile::ContextNode &Node);

revert_patches.txt

@@ -85,8 +85,6 @@ contact: RonL
 
 ---
 Reverts:
-7cfffe74 Unittests and usability for BitstreamWriter incremental flushing (#92983)
-993d2383e68b [ctx_prof] Remove `Buffer` field in PGOCtxProfWriter  
 1488fb415336 [PAC][AArch64] Lower ptrauth constants in code (#96879)  
 cc7308a1563e [ctx_prof] Make the profile output analyzable by llvm-bcanalyzer (#99563)
 c99bd3ce [ctx_prof] Extend `WorkloadImportsManager` to use the contextual profile (#98682)