[UI/UX:Forum] Improved Colors for Deleted Posts (Submitty#11184)

Closes Submitty#11165 

### What is the current behavior?
Currently, the deleted forum post background colors are hard to
differentiate from the standard posts, and they are not visually
appealing in dark mode.

### What is the new behavior?
Made the colors of deleted posts shades of blue. This distinguishes them
from active posts while also being a better fit for dark mode. Light
mode remains unchanged.

**Light Mode (Unchanged)**
![Screenshot 2025-02-07
215215](https://github.com/user-attachments/assets/a47ffc7b-836b-4f35-9ab3-0f69dc9fa76c)

**Dark Mode (Current Main)**
![Screenshot 2025-02-07
215847](https://github.com/user-attachments/assets/619644ad-e596-46e2-a447-dadad0ad4f8c)

**Dark Mode (Changed)**

![image](https://github.com/user-attachments/assets/467b7a32-960a-4eb9-a0a5-3601ed8a5ade)

**Summary of Changes**

![image](https://github.com/user-attachments/assets/e0197ad3-cd42-4c5a-b75b-9e4c2685c87d)

---------

Co-authored-by: Justin Manion <jmanion32@gmail.com>

Author: ryvaru

site/public/css/colors.css

@@ -127,7 +127,6 @@
     --btn-text-white: #ffffff;
     --btn-text-black: #000000;
     --btn-default-text: #2e2e2e;
-    --deleted-color: #000000;
 
     /* discussion forum */
     --deleted-and-unviewed-thread: #acc0d7;
@@ -243,7 +242,6 @@
 
 [data-black_mode="black"][data-theme="dark"] {
     --default-white: #000000;
-    --deleted-and-unviewed-thread: #939494;
     --background-blue: #000000;
     --default-black: #ffffff;
 
@@ -263,7 +261,6 @@
     /* might wanna change blue borders/hover text/sidebar text to submitty blue
       buttons, primarily but also can be used for notifications/anything
       that requires this color scheme */
-    --deleted-and-unviewed-thread: #939494;
     --standard-lightskyblue: #0975b9;
     --standard-mediumorchid: #b240ce;
     --default-white: #36393f;
@@ -314,6 +311,8 @@
     /* discussion forum */
     --attachment-box-color: #4a4a4a;
     --file-upload-table-hover: #4a4a4a;
+    --deleted-discussion-post-grey: #283E57;
+    --deleted-and-unviewed-thread: #3E5F7A;
 
     /* these differ from the colors on the posts for some reason?
           so I will put them here for reference

site/public/css/forum.css

@@ -798,12 +798,12 @@
 /* TODO: MAKE THIS CASCADE */
 .deleted {
     background-color: var(--deleted-discussion-post-grey);
-    color: var(--deleted-color);
+    color: var(--text-black);
 }
 
 .deleted-unviewed {
-    background-color: var(--deleted-and-unviewed-thread);
-    color: var(--deleted-color);
+    background-color: var(--deleted-and-unviewed-thread) !important;
+    color: var(--text-black) !important;
 }
 
 .deleted.active {