Finish converting GSL to absl::Span

One less dependency.

Change-Id: Iaac25a3c1312a21a8a2b77b8cfee2463bdb51196
Signed-off-by: Austin Schuh <austin.linux@gmail.com>
diff --git a/motors/peripheral/BUILD b/motors/peripheral/BUILD
index a42d502..7765ce1 100644
--- a/motors/peripheral/BUILD
+++ b/motors/peripheral/BUILD
@@ -45,7 +45,7 @@
     hdrs = ["uart_buffer.h"],
     visibility = ["//visibility:public"],
     deps = [
-        "//third_party/GSL",
+        "@com_google_absl//absl/types:span",
     ],
 )
 
@@ -72,7 +72,7 @@
         "//aos/containers:sized_array",
         "//motors:util",
         "//motors/core",
-        "//third_party/GSL",
+        "@com_google_absl//absl/types:span",
     ],
 )
 
@@ -99,6 +99,6 @@
         ":uart_buffer",
         "//motors:util",
         "//motors/core",
-        "//third_party/GSL",
+        "@com_google_absl//absl/types:span",
     ],
 )