revert(3p/git): Revert merge of git upstream at v2.26.2

This causes cgit to serve error pages, which is undesirable.

This reverts commit 5229c9b232, reversing
changes made to f2b211131f.

third_party/git/ci/test-documentation.sh

@@ -7,10 +7,7 @@
 
 filter_log () {
 	sed -e '/^GIT_VERSION = /d' \
-	    -e "/constant Gem::ConfigMap is deprecated/d" \
 	    -e '/^    \* new asciidoc flags$/d' \
-	    -e '/stripped namespace before processing/d' \
-	    -e '/Attributed.*IDs for element/d' \
 	    "$1"
 }