[roll pigweed] pw_env_setup: Remove dir_virtual_env GNI variable

Remove the dir_virtual_env GNI variable. The pw_env_setup_VIRTUAL_ENV
variable remains.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/103886

https://pigweed.googlesource.com/pigweed/pigweed
pigweed Rolled-Commits: 20cdc45b6974676..f8f2c9b63667116
Roller-URL: https://ci.chromium.org/b/8807010928405947057
Cq-Cl-Tag: roller-builder:pigweed-zephyr-roller
Cq-Cl-Tag: roller-bid:8807010928405947057
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: If99ee1283fbda01dd7335e5a5ca80935f63c5164
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/zephyr-integration/+/104342
Bot-Commit: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
Commit-Queue: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
diff --git a/pigweed b/pigweed
index 20cdc45..f8f2c9b 160000
--- a/pigweed
+++ b/pigweed
@@ -1 +1 @@
-Subproject commit 20cdc45b6974676efb0d0252483edd339a5f0696
+Subproject commit f8f2c9b636671165c1eda45e81f62db9e46fd229