Revert of Move ENABLE_PEPPER_CDMS to a buildflag header. (patchset #5 id:80001 of https://codereview.chromium.org/2411433002/ )

Reason for revert:
Broke build https://build.chromium.org/p/chromium.chrome/builders/Google%20Chrome%20Mac/builds/14706

Original issue's description:
> Move ENABLE_PEPPER_CDMS to a buildflag header.
>
> Removes the global build flag and #define and converts to a buildflag header in
> ppapi/features.
>
> A new target "//third_party/widevine/cdm:headers" was added since
> widevine_cdm_version.h was unreferenced in the build. Given that this file now
> requires //ppapi/features we really need "gn check" to work on it. I made the
> existing users of ":version_h" reference this new target which encompasses the
> public headers of the widevine CDM.
>
> TBR=jschuh (render_messages.h)
>
> Committed: https://crrev.com/e23a62a0c4b56618da615698717ed53983854f8d
> Cr-Commit-Position: refs/heads/master@{#424477}

TBR=jrummell@chromium.org,ddorwin@chromium.org,jschuh@chromium.org,brettw@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Review-Url: https://codereview.chromium.org/2412493003
Cr-Original-Commit-Position: refs/heads/master@{#424507}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 2d7d8a5e77ba0ee8c4c0e03a2ac4b15977926ca6
diff --git a/tools/gn/docs/cookbook.md b/tools/gn/docs/cookbook.md
index 66a44f7..623f84f 100644
--- a/tools/gn/docs/cookbook.md
+++ b/tools/gn/docs/cookbook.md
@@ -253,7 +253,7 @@
 | `enable_managed_users` (0/1)            | `enable_managed_users` (true/false)            | `//build/config/features.gni` |
 | `enable_mdns` (0/1)                     | `enable_mdns` (true/false)                     | `//build/config/features.gni` |
 | `enable_one_click_signin` (0/1)         | `enable_one_click_signin` (true/false)         | `//chrome/common/features.gni` |
-| `enable_pepper_cdms` (0/1)              | `enable_pepper_cdms` (true/false)              | `//ppapi/features/features.gni` |
+| `enable_pepper_cdms` (0/1)              | `enable_pepper_cdms` (true/false)              | `//build/config/features.gni` |
 | `enable_plugins` (0/1)                  | `enable_plugins` (true/false)                  | `//build/config/features.gni` |
 | `enable_plugin_installation` (0/1)      | `enable_plugin_installation` (true/false)      | `//build/config/features.gni` |
 | `enable_basic_printing` (0/1)           | `enable_basic_printing` (true/false)           | `//build/config/features.gni` |