Fix logo height in doc navbar

Author: dstansby

docs/_static/custom.css

@@ -1,12 +1,5 @@
 @import url('https://fonts.googleapis.com/css2?family=Lato:ital,wght@0,400;0,700;0,900;1,400;1,700;1,900&family=Open+Sans:ital,wght@0,400;0,600;1,400;1,600&display=swap');
 
-.navbar-brand img {
-   height: 75px;
-}
-.navbar-brand {
-   height: 75px;
-}
-
 body {
   font-family: 'Open Sans', sans-serif;
 }