Convert px units to rem for typography variables.

[shinokada]

Describe the bug
A clear and concise description of what the bug is.

The comment "rem pls" at Line 13 indicates awareness that these typography variables should use rem units instead of px. Using px prevents proper scaling with user font-size preferences and impacts accessibility.

   /* TEXT VARIABLES */
   --text-2xs: 0.625rem;
   --spacing-8xl: 90rem;
-  --leading-9: 36px; /* rem pls */
-  --leading-7: 28px;
-  --leading-8: 32px;
-  --leading-6: 24px;
-  --leading-4: 16px;
-  --leading-none: 1px;
-  --leading-5: 20px;
-  --tracking-tighter: -0.8px;
-  --leading-heading-none: 60px;
-  --tracking-tight: -0.4px;
+  --leading-9: 2.25rem;
+  --leading-7: 1.75rem;
+  --leading-8: 2rem;
+  --leading-6: 1.5rem;
+  --leading-4: 1rem;
+  --leading-none: 0.0625rem;
+  --leading-5: 1.25rem;
+  --tracking-tighter: -0.05rem;
+  --leading-heading-none: 3.75rem;
+  --tracking-tight: -0.025rem;

[ninjadevpunk]

Just to confirm all the leading custom properties need rem conversion or only the line pertaining to the 9 variant?