[torque] Use char newline character instead of string

Currently, when GeneratePrintDefinitionsForClass generates its Print
functions it uses a string literal as the newline character for all the
last lines. For example:

void TorqueGeneratedStruct<Struct, HeapObject>::StructPrint(
    std::ostream& os) {
  this->PrintHeader(os, "TorqueGeneratedStruct");
  os << "\n";
}

The last line could use a single character instead of a string,
for example:

void TorqueGeneratedStruct<Struct, HeapObject>::StructPrint(
    std::ostream& os) {
  this->PrintHeader(os, "TorqueGeneratedStruct");
  os << '\n';
}

The commit suggests changing this into a char.

Change-Id: Id7a2f5fb17108fcbb543109d18b6b474ac1c5d2d
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2108546Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66788}

src/torque/implementation-visitor.cc

@@ -4037,7 +4037,7 @@ void GeneratePrintDefinitionsForClass(std::ostream& impl, const ClassType* type,
       }
     }
   }
-  impl << "  os << \"\\n\";\n";
+  impl << "  os << '\\n';\n";
   impl << "}\n\n";
 }
 }  // namespace