docs: drop period in headers

We don't do this in most places, so standardize the outliers.

Change-Id: I80c1ef16c5fa7355dcb7797bc8e56852b22c24d5
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/583641
Tested-by: Mike Frysinger <vapier@google.com>
Commit-Queue: Mike Frysinger <vapier@google.com>
Reviewed-by: Gavin Mak <gavinmak@google.com>

CONTRIBUTING.md

diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index d3c0142..0657414 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -24,7 +24,7 @@
 yourself with the following relevant bits.
 
 
-## Make separate commits for logically separate changes.
+## Make separate commits for logically separate changes
 
 Unless your patch is really trivial, you should not be sending out a patch that
 was generated between your working tree and your commit head.
@@ -118,7 +118,7 @@
 has been applied and pushed out.
 
 
-## Sending your patches.
+## Sending your patches
 
 Do not email your patches to anyone.
 

docs/windows.md

diff --git a/docs/windows.md b/docs/windows.md
index 5759445..1b9f0c5 100644
--- a/docs/windows.md
+++ b/docs/windows.md
@@ -145,7 +145,7 @@
 
 [mintty]: https://github.com/mintty/mintty/issues/56
 
-### repohooks always fail with an close_fds error.
+### repohooks always fail with an close_fds error
 
 When using the [reference repohooks project][repohooks] included in AOSP,
 you might see errors like this when running `repo upload`: