pigweed: update workflows.json

The new version of Pigweed's Bazel workflow driver automatically
appends the end-of-options marker ( -- ) before the list of targets.
Because  workflows.json  also explicitly defined  "--"  in the  args
array for several Bazel build configurations, the resulting command
contained double markers.

Signed-off-by: Chris Frantz <cfrantz@google.com>

workflows.json

diff --git a/workflows.json b/workflows.json
index 261827c..a616a84 100644
--- a/workflows.json
+++ b/workflows.json
@@ -15,8 +15,7 @@
       "build_type": "bazel",
       "args": [
         "--keep_going",
-        "--build_tag_filters=-hardware,-disabled",
-        "--"
+        "--build_tag_filters=-hardware,-disabled"
       ],
       "env": {},
       "driver_options": {
@@ -42,8 +41,7 @@
         "build_type": "bazel",
         "args": [
           "--aspects=@rules_rust//rust:defs.bzl%rust_clippy_aspect",
-          "--output_groups=clippy_checks",
-          "--"
+          "--output_groups=clippy_checks"
         ],
         "driver_options": {
           "@type": "pw.build.proto.BazelDriverOptions",
@@ -65,8 +63,7 @@
           "--keep_going",
           "--build_tag_filters=-hardware,-disabled,-verilator,-emulator,-qemu",
           "--test_tag_filters=-hardware,-disabled,-verilator,-emulator,-qemu",
-          "--test_output=streamed",
-          "--"
+          "--test_output=streamed"
         ],
         "driver_options": {
           "@type": "pw.build.proto.BazelDriverOptions",