aconfig: remove reference to non-existent workspace member "aconfig_storage_write_api"

Commit bca2f3c28ca incorrectly added "aconfig_storage_write_api" as a
workspace member even though that project has not yet been created. This
broke cargo.

Unbreak cargo by removing "aconfig_storage_write_api".

Bug: N/A
Test: croot build/make/tools/aconfig && cargo c
Change-Id: Ic0f71a53d49736228a376f64808aea24c2ec8ce5
diff --git a/tools/aconfig/Cargo.toml b/tools/aconfig/Cargo.toml
index 6bd0d06..7112fd4 100644
--- a/tools/aconfig/Cargo.toml
+++ b/tools/aconfig/Cargo.toml
@@ -5,7 +5,6 @@
     "aconfig_protos",
     "aconfig_storage_file",
     "aconfig_storage_read_api",
-    "aconfig_storage_write_api",
     "aflags",
     "printflags"
 ]