Revert "[lldb/DWARF] Search fallback to the manual index in GetFullyQualified… (#102123)"

The test appears to be flaky. Revert it while I investigate.

This reverts commits 7027cc6 and
21ef272.

Author: labath

lldb/source/Plugins/SymbolFile/DWARF/DebugNamesDWARFIndex.cpp

@@ -371,7 +371,6 @@ void DebugNamesDWARFIndex::GetFullyQualifiedType(
         !ProcessEntry(entry, callback))
       return;
   }
-  m_fallback.GetFullyQualifiedType(context, callback);
 }
 
 bool DebugNamesDWARFIndex::SameParentChain(

lldb/test/Shell/SymbolFile/DWARF/x86/dwp-hash-collision.s

@@ -3,9 +3,6 @@
 ## split unit from the DWP file. This can sometimes happen when the compile unit
 ## is nearly empty (e.g. because LTO has optimized all of it away).
 
-# Is flaky on Windows on Arm.
-# UNSUPPORTED: system-windows
-
 # RUN: llvm-mc -triple=x86_64-pc-linux -filetype=obj %s --defsym MAIN=0 > %t
 # RUN: llvm-mc -triple=x86_64-pc-linux -filetype=obj %s > %t.dwp
 # RUN: %lldb %t -o "image lookup -t my_enum_type" \