[roll third_party/pigweed] pw_function: Rename template parameter

Rename Callable to FunctionType, since the parameter should be a
function type, such as void(int, bool), rather than a callable type.
This matches fit::function's naming.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/168334

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 083d16a55349fd0..9e0760ff9b75fbd
Roller-URL: https://ci.chromium.org/b/8771940723762633873
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I1bff35ad8eca17cb15e5c1e962dec2a6bc2e0e14
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/168336
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 083d16a..9e0760f 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 083d16a55349fd015c3f601eec77dd7c76a7e4f3
+Subproject commit 9e0760ff9b75fbd720a93945f405481b0371d69c