Remove obsolete "link_pool" code from GN's ninja writer.

tools/gn/ninja_toolchain_writer.cc

Index: tools/gn/ninja_toolchain_writer.cc
diff --git a/tools/gn/ninja_toolchain_writer.cc b/tools/gn/ninja_toolchain_writer.cc
index 27e2e0c908d968d6ec3f417229bd9eb8a13236f4..a48a8b9f84679448814b0d06e8c65b3855fe7c08 100644
--- a/tools/gn/ninja_toolchain_writer.cc
+++ b/tools/gn/ninja_toolchain_writer.cc
@@ -110,12 +110,6 @@ void NinjaToolchainWriter::WriteToolRule(const Toolchain::ToolType type,
     std::string pool_name =
         tool->pool().ptr->GetNinjaName(settings_->default_toolchain_label());
     out_ << kIndent << "pool = " << pool_name << std::endl;
-  } else if (type == Toolchain::TYPE_SOLINK ||
-      type == Toolchain::TYPE_SOLINK_MODULE ||
-      type == Toolchain::TYPE_LINK) {
-    // The link pool applies to linker tools. Don't count TYPE_ALINK since
-    // static libraries are not generally intensive to write.
-    out_ << kIndent << "pool = link_pool\n";
   }
 
   if (tool->restat())