Switch logo color in docs pages to dark blue

The trademark for the logo, as filed, is specified as dark blue.
That logo needs to be displayed in a user guide or manual or
alongside a direct download of the software in order to demonstrate
continued use of the mark, and the foundation's trademark lawyers
have expressed concern that a white version is insufficient (but
they seem to be okay with the current background color as long as
the lines of the logo are colored similar to the version on file).

This is a copy of the equivalent change from the zuul repository.

Co-Authored-By: James E. Blair <jim@acmegating.com>
Depends-On: https://review.opendev.org/934443
Change-Id: I5bc28f0117e26e451f77fb0946ee1de44beb6852

doc/source/_static/logo.svg

@@ -51,36 +51,29 @@
 </style>
 <g
    id="g1639"
-   transform="matrix(9.2592535,0,0,9.2592535,-316.66647,-399.99975)"
-   style="fill:#ffffff;fill-opacity:1">
+   transform="matrix(9.2592535,0,0,9.2592535,-316.66647,-399.99975)">
 	<path
    class="st0"
    d="m 34.2,100.8 h 66.5 L 86.5,76.2 v -8.4 l 3.9,-5.1 H 78.6 L 67.4,43.2 56.2,62.7 H 44.4 l 3.9,5.1 v 8.4 z M 48.4,97.4 H 40 l 8.4,-14.5 z m 5.7,0 H 51.7 V 77.6 h 2.4 z m 0,-23.1 h -2.4 v -2.4 h 2.4 z M 65.7,97.4 H 57.5 V 77.6 h 8.2 z m 11.6,0 H 69.1 V 77.6 h 8.2 z m 0,-23.1 H 57.5 v -2.4 h 19.8 z m 5.8,23.1 H 80.7 V 77.6 h 2.4 z m 0,-23.1 h -2.4 v -2.4 h 2.4 z m 3.4,8.6 8.4,14.5 h -8.4 z m -19.1,-33 7.4,12.7 H 60 Z M 83.6,66 83.1,66.7 v 1.8 H 51.7 V 66.7 L 51.2,66 Z"
-   id="path1627"
-   style="fill:#ffffff;fill-opacity:1" />
+   id="path1627" />
 	<g
-   id="g1637"
-   style="fill:#ffffff;fill-opacity:1">
+   id="g1637">
 		<polygon
    class="st0"
    points="227.5,86 250.2,86 246.7,80 233.5,80 233.5,57.2 227.5,60.7 "
-   id="polygon1629"
-   style="fill:#ffffff;fill-opacity:1" />
+   id="polygon1629" />
 		<path
    class="st0"
    d="m 207.5,74.2 v 0 0 c 0,3.6 -2.9,6.5 -6.5,6.5 -3.6,0 -6.5,-2.9 -6.5,-6.5 v 0 0 -17 l -6,3.5 v 13.5 0 c 0,6.9 5.6,12.5 12.5,12.5 6.9,0 12.5,-5.6 12.5,-12.5 v 0 -17 l -6,3.5 z"
-   id="path1631"
-   style="fill:#ffffff;fill-opacity:1" />
+   id="path1631" />
 		<path
    class="st0"
    d="m 168.4,74.2 v 0 0 c 0,3.6 -2.9,6.5 -6.5,6.5 -3.6,0 -6.5,-2.9 -6.5,-6.5 v 0 0 -17 l -6,3.5 v 13.5 0 c 0,6.9 5.6,12.5 12.5,12.5 6.9,0 12.5,-5.6 12.5,-12.5 v 0 -17 l -6,3.5 z"
-   id="path1633"
-   style="fill:#ffffff;fill-opacity:1" />
+   id="path1633" />
 		<polygon
    class="st0"
    points="110.4,86 131.9,86 135.4,80 120.8,80 133.9,57.2 113.8,57.2 110.4,63.3 123.5,63.3 "
-   id="polygon1635"
-   style="fill:#ffffff;fill-opacity:1" />
+   id="polygon1635" />
 	</g>
 </g>
 </svg>

doc/source/conf.py

@@ -100,6 +100,7 @@ html_theme_options = {
     'collapse_navigation': False,
     'navigation_depth': -1,
     'logo_only': True,
+    'style_nav_header_background': '#41B6E6',
 }
 
 html_context = {