Remove reduz from some autorequested code reviews

He's still one of the main architects of some of these code branches,
but quite often PRs that modify one or two files in such folders don't
necessarily need his input, and he has enough backlog to handle.

PR triagers will ask for his review manually whenever relevant. He's
left as code owner for physics/visual servers and rendering backends.

CODEOWNERS

@@ -2,8 +2,6 @@
 # Each line is a file pattern followed by one or more owners.
 # Owners can be @users, @org/teams or emails
 
-/core/               @reduz
-
 /doc/                @godotengine/documentation
 doc_classes/*        @godotengine/documentation
 
@@ -22,22 +20,19 @@ doc_classes/*        @godotengine/documentation
 /drivers/winmidi/    @marcelofg55
 /drivers/xaudio2/    @marcelofg55
 
-# Porting
-/drivers/unix/       @reduz @hpvb
-/drivers/windows/    @reduz @hpvb
+/drivers/unix/       @hpvb
+/drivers/windows/    @hpvb
 
 /editor/icons/       @djrm
 
-/main/               @reduz
-
 /misc/               @akien-mga
 
 /modules/bullet/     @AndreaCatania
-/modules/csg/        @reduz @BastiaanOlij
+/modules/csg/        @BastiaanOlij
 /modules/enet/       @godotengine/network
 /modules/gdnative/   @karroffel
 /modules/gdnative/*arvr/ @BastiaanOlij
-/modules/gdscript/   @reduz @vnen @bojidar-bg
+/modules/gdscript/   @vnen @bojidar-bg
 /modules/mbedtls/    @godotengine/network
 /modules/mobile_vr/  @BastiaanOlij
 /modules/mono/       @neikeq
@@ -49,8 +44,6 @@ doc_classes/*        @godotengine/documentation
 /platform/javascript/ @eska014
 /platform/uwp/       @vnen
 
-/scene/main/         @reduz
-
 /server/physics*/    @reduz @AndreaCatania
 /server/visual*/     @reduz @karroffel