fix comments

I had it all backwards: DrRacket went from "increment" to Greek
capital delta (which makes a lot more sense).

collects/mrlib/tex-table.rkt

@@ -92,7 +92,7 @@
     ("Lambda" "Λ")
     ("Sigma" "Σ")
     ("Psi" "Ψ")
-    ("Delta" "Δ") ; <- this character is Unicode "increment", not Greek delta
+    ("Delta" "Δ")
     ("Xi" "Ξ")
     ("Upsilon" "Υ")
     ("Omega" "Ω")

collects/scribble/latex-render.rkt

@@ -853,7 +853,7 @@
                             [(#\♭) "$\\flat$"]
                             [(#\♮) "$\\natural$"]
                             [(#\√) "$\\surd$"]
-                            [(#\Δ) "$\\Delta$"] ; no better mapping for than \Delta for "increment"
+                            [(#\∆) "$\\Delta$"] ; no better mapping for than \Delta for "increment"
                             [(#\u2211) "$\\sum$"] ; better than \Sigma, right?
                             [(#\u220F) "$\\prod$"] ; better than \Pi, right?
                             [(#\u2210) "$\\coprod$"]
@@ -881,7 +881,7 @@
                             [(#\ξ) "$\\xi$"]
                             [(#\Γ) "$\\Gamma$"]
                             [(#\Ψ) "$\\Psi$"]
-                            [(#\∆) "$\\Delta$"]
+                            [(#\Δ) "$\\Delta$"]
                             [(#\Ξ) "$\\Xi$"]
                             [(#\Υ) "$\\Upsilon$"]
                             [(#\Ω) "$\\Omega$"]