player: drop talent-side modCastingTime fudge from haste display

The player frame's "Effective Haste" mode was hardcoded talent-position
scrapes: GetTalentInfo(1, 16) for the Mage "Accelerated Arcana"
(flat 5%) and GetTalentInfo(1, 14) for the Warlock "Rapid Deterioration"
(3% per rank), folded into the displayed haste % via
`(1 / (modCastSpeed * modCastingTime) - 1) * 100`.

That's two problems in one:
- Hardcoded talent indices and effect percentages — brittle to any
  Turtle tree reshuffle or retune.
- Conceptually muddled: it folds gear-haste and talent-cast-reduction
  into one number that's hard to read as anything specific. The actual
  effective cast time is already shown on the cast bar via
  C_Spell.UnitCastingInfo (engine helper accounts for SpellMod op 10).

Drop modCastingTime, the LEARNED_SPELL_IN_TAB watcher frame that
maintained it, the per-class talent scrape, and the hasteMode == "2"
display branch. Collapse the now-binary "display_haste" config from a
3-option dropdown to a checkbox. Users on legacy "2" will see the
checkbox unchecked once and can re-enable with a single click.

modules/gui.lua

@@ -2380,11 +2380,7 @@ pfUI:RegisterModule("gui", function ()
 
         if c == "player" then
           CreateConfig(nil, T["Player SP/Haste Display"], nil, nil, "header")
-          CreateConfig(nil, T["Haste Display"], C.unitframes[c], "display_haste", "dropdown", {
-            "0:"..T["None"],
-            "1:"..T["Haste (cast speed increase)"],
-            "2:"..T["Effective Haste (Haste * cast time reduction)"], -- Only affects mages/warlocks I believe
-          })
+          CreateConfig(nil, T["Haste Display"], C.unitframes[c], "display_haste", "checkbox")
           CreateConfig(nil, T["Haste Display Color"], C.unitframes[c], "display_haste_color", "color")
           CreateConfig(nil, T["Display Spell Power"], C.unitframes[c], "display_spellpower", "checkbox")
           CreateConfig(nil, T["Use Custom Spell Power Color (unchecked = biggest school color)"], C.unitframes[c], "display_sp_color_override", "checkbox")