test: do not dedent() in feed() (#32884)

Most callers of feed() do not expect feed() to dedent.
Now use a literal space in tests where it looks better.

test/functional/testnvim.lua

@@ -366,7 +366,7 @@ end
 --- @param ... string
 function M.feed(...)
   for _, v in ipairs({ ... }) do
-    nvim_feed(dedent(v))
+    nvim_feed(v)
   end
 end
 
@@ -615,7 +615,7 @@ function M.insert(...)
   nvim_feed('i')
   for _, v in ipairs({ ... }) do
     local escaped = v:gsub('<', '<lt>')
-    M.feed(escaped) -- This also dedents :P
+    nvim_feed(dedent(escaped))
   end
   nvim_feed('<ESC>')
 end