Knip 7: remove unused style constants (#1777)

## Summary:
I could see an argument for keeping these since they define a palette we could choose from. However, we're trying to more closely align with WB so I think we should think of that as our palette rather than maintaining our own.

Author: handeyeco

Reviewers: benchristel

Required Reviewers:

Approved By: benchristel

Checks: ✅ Publish npm snapshot (ubuntu-latest, 20.x), ✅ Cypress (ubuntu-latest, 20.x), ✅ Check builds for changes in size (ubuntu-latest, 20.x), ✅ Lint, Typecheck, Format, and Test (ubuntu-latest, 20.x), ✅ Publish Storybook to Chromatic (ubuntu-latest, 20.x), ✅ Check for .changeset entries for all changed files (ubuntu-latest, 20.x), ✅ gerald

Pull Request URL: #1777

.changeset/proud-ligers-learn.md

@@ -0,0 +1,5 @@
+---
+"@khanacademy/perseus": patch
+---
+
+Remove unused styles constants

packages/perseus/src/styles/constants.ts

@@ -2,38 +2,15 @@
 export const baseFontFamily = "'Lato', sans-serif";
 // @boldFontFamily:        "Lato-Bold", "Lato", sans-serif;
 export const boldFontFamily = "'Lato-Bold', 'Lato', sans-serif";
-// @green:                 #76a005;
-export const green = "#76A005";
 // @kaGreen:               #71b307;
 export const kaGreen = "#71B307";
-// @blue:                  #1c758a;
-export const blue = "#1C758A";
-// @gray:                  #aaa;
-export const gray = "#AAAAAA";
-// @red:                   #ffbaba;
-export const red = "#FFBABA";
-// @grayLight:             #aaa;
-export const grayLight = "#AAAAAA";
-// @grayLighter:           #ddd;
-export const grayLighter = "#DDDDDD";
-// @learnstormBlue:        #4898fc;
-export const learnstormBlue = "#4898FC";
 
 export const white = "#FFFFFF";
-export const gray98 = "#FAFAFA";
 export const gray97 = "#F6F7F7";
-export const gray95 = "#F0F1F2";
-export const gray90 = "#E3E5E6";
 export const gray85 = "#D6D8DA";
 export const gray76 = "#BABEC2";
 export const gray68 = "#888D93";
-export const gray41 = "#626569";
-export const gray25 = "#3B3e40";
 export const gray17 = "#21242c";
-export const black = "#000000";
-
-export const warning1 = "#F86700";
-export const warning3 = "#C75300";
 
 // @pure-sm-min: 568px;
 export const pureSmMin = "568px";
@@ -53,16 +30,10 @@ export const pureMdMax = "1023px";
 export const pureLgMax = "1279px";
 // @tableBackgroundAccent: #f9f9f9; // for striping
 export const tableBackgroundAccent = "#F9F9F9";
-// @zIndexScratchPad: 1;
-export const zIndexScratchPad = 1;
 // @zIndexAboveScratchpad: @zIndexScratchPad + 1;
 export const zIndexAboveScratchpad = 2;
 // @zIndexInteractiveComponent: @zIndexAboveScratchpad + 1;
 export const zIndexInteractiveComponent = 3;
-// @zIndexCurrentlyDragging: @zIndexInteractiveComponent + 1;
-export const zIndexCurrentlyDragging = 4;
-// @zIndexCalculator: @zIndexCurrentlyDragging + 1;
-export const zIndexCalculator = 5;
 // @phoneMargin: 16px;
 export const phoneMargin = 16;