feedback: Increase text contrast in main dialog.

The text contrast was previously either far too low or borderline too
low for all text. This CL makes the default text darker and uses the
same color for the legal/privacy paragraph as the rest of the text.

BUG=chromium:1005543
TEST=Take screenshot (on eve), check with color contrast companion.

Change-Id: I791a79c92238f4b65f3e9e52c917104b153a82dd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1864363Reviewed-by: Ian Barkley-Yeung <iby@chromium.org>
Reviewed-by: Jeffrey Kardatzke <jkardatzke@google.com>
Reviewed-by: J Kardatzke <jkardatzke@chromium.org>
Commit-Queue: Miriam Zimmerman <mutexlox@chromium.org>
Cr-Commit-Position: refs/heads/master@{#707139}

chrome/browser/resources/feedback/css/feedback.css

@@ -43,7 +43,7 @@ body {
 }
 
 .content {
-  color: #646464;
+  color: #444;
   flex-grow: 1;
   font-size: 12px;
   margin: 20px;
@@ -149,7 +149,6 @@ body {
 }
 
 .content #privacy-note {
-  color: #969696;
   font-size: 12px;
   line-height: 20px;
   margin-bottom: 0;