Swap light/dark mode colors for span_green (#96378)

## About The Pull Request

The light mode colors for `span_green` are bright and hard to read,
whereas the dark mode ones are weirdly dark, so I swapped them.

<img width="289" height="79" alt="image"
src="https://github.com/user-attachments/assets/65a8f064-7ecb-461f-8d5f-4d85cf49ab97"
/>


## Why It's Good For The Game

Improve text contrast in light mode

## Changelog

idk

tgui/packages/tgui-panel/styles/tgchat/chat-dark.scss

@@ -567,7 +567,7 @@ em {
 }
 
 .green {
-  color: hsl(132.8, 93.4%, 29.6%);
+  color: hsl(132.9, 100%, 50.6%);
 }
 
 .grey {

tgui/packages/tgui-panel/styles/tgchat/chat-light.scss

@@ -585,7 +585,7 @@ h2.alert {
 }
 
 .green {
-  color: hsl(132.9, 100%, 50.6%);
+  color: hsl(132.8, 93.4%, 29.6%);
 }
 
 .grey {