Stop using `group_static_libs` property

This property is now ignored, so there is no need to set it.
For more details, see the bug and/or "Effecient archive file handling"
in https://lld.llvm.org/NewLLD.html#key-concepts

Bug: 189475744
Test: Manual build succeeds
Change-Id: I411cfaf6d54b2c728b1cd073a2f588ab9aa89843
diff --git a/gn/gn_to_bp.py b/gn/gn_to_bp.py
index 8174a32..bdba64e 100644
--- a/gn/gn_to_bp.py
+++ b/gn/gn_to_bp.py
@@ -181,7 +181,6 @@
         "libwebp-decode",
         "libwebp-encode",
     ],
-    group_static_libs: true,
     target: {
       android: {
         shared_libs: [