Update preferences.md to reflect v3 scheduler availability (#210)

* Update preferences.md to reflect v3 scheduler availability

Text updated to reflect availability of v3 scheduler on all platforms.

* Update preferences.md

Modification of old parameters that are no longer displayed and addition of the new ones.

* Update src/preferences.md

Correct plural.

src/preferences.md

@@ -50,19 +50,6 @@ These options allow you to remove some unnecessary elements from the screen duri
 
 ### Scheduler
 
-**v3 Scheduler**\
-Using the Anki v3 scheduler is recommended if you don't use AnkiDroid. It's documented here:\
-<https://faqs.ankiweb.net/the-2021-scheduler.html>
-
-**Show learning cards with larger steps before**\
-Only shown when the 2.1 scheduler is enabled. Normally learning cards with a 1+
-day delay are shown after normal reviews. If checked, Anki will show them before
-normal reviews instead.
-
-**Legacy timezone handling**\
-Please see here:
-<https://faqs.ankiweb.net/timezone-handling-changes.html>
-
 **Next day starts at**\
 Controls when Anki should start showing the next day’s cards. The default
 setting of 4AM ensures that if you’re studying around midnight, you won’t have
@@ -86,10 +73,6 @@ as a 30 minute study session) into smaller blocks. If you set the timebox time
 limit to a non-zero number of minutes, Anki will periodically show you how many
 cards you’ve managed to study during the prescribed time limit.
 
-**Mix new cards and reviews**:
-Only shown when the v1/v2 schedulers are enabled. This drop-down box controls when
-new cards are shown: either mixed with, before, or after all reviews.
-
 ### Review
 
 **Show play buttons on cards with audio**\
@@ -106,6 +89,9 @@ Disable this option to hide the card count at the bottom of the screen.
 **Show next review time above answer buttons**\
 Useful to know how far in the future your cards are being pushed.
 
+**Spacebar (or enter) also answers card**\
+Defines whether a press on the space bar (or the enter key) also answers cards.
+
 ## Editing
 
 ### Editing