Fix luminosity contrast ratio for placeholder text for edit fields in user agent client hints section

Bug: 448420942
Change-Id: I2f705ff27883f4dd3cea4dd9aa9bb1fe193b68c0
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/7001545
Reviewed-by: Kim-Anh Tran <[email protected]>
Commit-Queue: Sylvester Elorm Coch <[email protected]>

Author: ElormCoch

front_end/panels/settings/emulation/components/userAgentClientHintsForm.css

@@ -86,6 +86,10 @@ hr.section-separator {
   height: 18px;
 }
 
+.input-field::placeholder {
+    color: var(--sys-color-on-surface-subtle);
+}
+
 .input-field:focus {
   border: 1px solid var(--sys-color-state-focus-ring);
   outline-width: 0;