bpo-31569: correct PCBuild/ case to PCbuild/ in build scripts and docs (GH-3711)

diff --git a/.github/CODEOWNERS b/.github/CODEOWNERS
index 28ca17e..67c03a8 100644
--- a/.github/CODEOWNERS
+++ b/.github/CODEOWNERS
@@ -35,7 +35,7 @@
 
 # Windows
 /PC/                          @python/windows-team
-/PCBuild/                     @python/windows-team
+/PCbuild/                     @python/windows-team
 
 # Windows installer packages
 /Tools/msi/                   @python/windows-team