gpui: Fix SVG color render, when color have alpha (#20537)

Release Notes:

- N/A


## Demo

- [Source
SVG](https://github.com/user-attachments/assets/1c681e01-baba-4613-a3e7-ea5cb3015406)
click here open in browser.

| Before | After |
| --- | --- |
| <img width="1212" alt="image"
src="https://github.com/user-attachments/assets/ba323b13-538b-4a34-bb64-9dcf490aface">
| <img width="1212" alt="image"
src="https://github.com/user-attachments/assets/4635926a-843e-426d-89a1-4e9b4f4cc37e">
|

---------

Co-authored-by: Floyd Wang <gassnake999@gmail.com>

crates/gpui/examples/image/color.svg

@@ -6,8 +6,8 @@
     <circle cx="240" cy="100" r="30" stroke="#dc2626" />
     <circle cx="380" cy="100" r="20" stroke="#d97706" />
     <circle cx="380" cy="240" r="30" stroke="#06b6d4" />
-    <circle cx="100" cy="240" r="30" stroke="#3b82f6" />
+    <circle cx="100" cy="240" r="30" stroke="#3b82f666" />
     <circle cx="240" cy="380" r="30" stroke="#7c3aed" />
     <circle cx="380" cy="380" r="20" stroke="#c026d3" />
-    <circle cx="100" cy="380" r="20" stroke="#e11d48" />
-</svg>
+    <circle cx="100" cy="380" r="20" stroke="#e11d4866" />
+</svg>