migrations: drop old documentation

Change-Id: Ib994a14c1a8e9af1f8d0b293924bf36b1fbbd8f2
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/315130
Trust: Julie Qiu <julie@golang.org>
Run-TryBot: Julie Qiu <julie@golang.org>
TryBot-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Jamal Carvalho <jamal@golang.org>

migrations/000092_drop_old_documentation.down.sql

@@ -0,0 +1,17 @@
+-- Copyright 2021 The Go Authors. All rights reserved.
+-- Use of this source code is governed by a BSD-style
+-- license that can be found in the LICENSE file.
+
+BEGIN;
+
+CREATE TABLE old_documentation (
+    unit_id INTEGER NOT NULL,
+    goos TEXT NOT NULL,
+    goarch TEXT NOT NULL,
+    synopsis TEXT NOT NULL,
+    source BYTEA,
+    PRIMARY KEY (unit_id, goos, goarch),
+    FOREIGN KEY (unit_id) REFERENCES units(id) ON DELETE CASCADE
+);
+
+END;

migrations/000092_drop_old_documentation.up.sql

@@ -0,0 +1,9 @@
+-- Copyright 2021 The Go Authors. All rights reserved.
+-- Use of this source code is governed by a BSD-style
+-- license that can be found in the LICENSE file.
+
+BEGIN;
+
+DROP TABLE old_documentation;
+
+END;