[disassembler] Add back missing whitespaces

This adds back two spaces that went missing in
https://crrev.com/c/2978252, removing the space between offset and
instruction bytes.

After https://crrev.com/c/2978252:
0x21ea0e1e04a0     055             push rbp
0x21ea0e1e04a1     14889e5         REX.W movq rbp,rsp

After this CL:
0x2be7c8c604a0     0  55           push rbp
0x2be7c8c604a1     1  4889e5       REX.W movq rbp,rsp

R=delphick@chromium.org

Change-Id: I6df35aed9b5909da72965fef622b07120c226fae
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2996199Reviewed-by: Dan Elphick <delphick@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75472}

src/diagnostics/disassembler.cc

@@ -365,7 +365,7 @@ static int DecodeIt(Isolate* isolate, ExternalReferenceEncoder* ref_encoder,
       out << "\033[33;1m";
     }
     out << static_cast<void*>(prev_pc) << "  " << std::setw(4)
-        << prev_pc - begin;
+        << prev_pc - begin << "  ";
 
     // Instruction.
     out << decode_buffer.begin();