Revert "Merge branch 'jn/reftable-doc' into next"

This reverts commit e128adb, reversing
changes made to 39ad6ee, as the doc is
better polished within the rest of the topic hn/reftable.

Author: gitster

Documentation/Makefile

@@ -92,7 +92,6 @@ TECH_DOCS += technical/protocol-capabilities
 TECH_DOCS += technical/protocol-common
 TECH_DOCS += technical/protocol-v2
 TECH_DOCS += technical/racy-git
-TECH_DOCS += technical/reftable
 TECH_DOCS += technical/send-pack-pipeline
 TECH_DOCS += technical/shallow
 TECH_DOCS += technical/signature-format