Disable the legacy ReaderRotation module (#12309)

AFAICT, this has never worked since the KPV -> KOReader refactor, as it relies on a weird little DrawContext "feature", while the actually in-use rotation framework is handled via BlitBuffer.

That kludge pollutes *a lot* of both the backend and frontend code, so I plan to annihilate that in a followup PR.

See #12303 for more context

frontend/apps/reader/readerui.lua

@@ -44,7 +44,7 @@ local ReaderLink = require("apps/reader/modules/readerlink")
 local ReaderMenu = require("apps/reader/modules/readermenu")
 local ReaderPageMap = require("apps/reader/modules/readerpagemap")
 local ReaderPanning = require("apps/reader/modules/readerpanning")
-local ReaderRotation = require("apps/reader/modules/readerrotation")
+--local ReaderRotation = require("apps/reader/modules/readerrotation")
 local ReaderPaging = require("apps/reader/modules/readerpaging")
 local ReaderRolling = require("apps/reader/modules/readerrolling")
 local ReaderSearch = require("apps/reader/modules/readersearch")
@@ -160,12 +160,15 @@ function ReaderUI:init()
         view = self.view,
         ui = self
     })
-    -- rotation controller
+    -- (legacy, and defunct) rotation controller
+    --- @fixme: Tripping this would break rendering, c.f., `Document:renderPage`
+    --[[
     self:registerModule("rotation", ReaderRotation:new{
         dialog = self.dialog,
         view = self.view,
         ui = self
     })
+    --]]
     -- Handmade/custom ToC and hidden flows
     self:registerModule("handmade", ReaderHandMade:new{
         dialog = self.dialog,