Fix various issues with Markdown docs

- Removed links to old wiki pages
- Fixed broken table in test_descriptions.md
- Fixed tables that don't have heading
- Fix codeblock in common_build_tasks.md

Review URL: https://codereview.chromium.org/1473953002

Cr-Commit-Position: refs/heads/master@{#361773}
diff --git a/docs/shift_based_development.md b/docs/shift_based_development.md
index 3d8f645..ffc62c9 100644
--- a/docs/shift_based_development.md
+++ b/docs/shift_based_development.md
@@ -58,9 +58,7 @@
 pull (which in our git svn repositories behind the scenes does a `git svn fetch` etc.
 
 Shift-based collaboration won't work well (at least not with a
-pipeline of branches) unless you are using an "unmanaged" git checkout
-(search for "unmanaged" on
-[this page](https://code.google.com/p/chromium/wiki/UsingNewGit)).
+pipeline of branches) unless you are using an "unmanaged" git checkout.
 
 ## Example Working Rules
 
@@ -149,4 +147,4 @@
 To push all "matching" branches (i.e. push the latest copy of
 any local branch that has previously been pushed to shiftrepo): `git push shiftrepo`
 
-To delete a branch from shiftrepo, it's weird: `git push shiftrepo :branchname`
\ No newline at end of file
+To delete a branch from shiftrepo, it's weird: `git push shiftrepo :branchname`