RFR: 8334241: Adjust API docs side bar dimensions

[Hannes Wallnöfer]

Please review a change to slightly adjust the proportion between the side bar and the main content area in API documentation pages, making the side bar a bit slimmer and leaving more space for the main content area. The ratio between side bar and main content used to be 1 : 2.6, it is now 1 : 3. 

Updated API documentation[ can be viewed here](https://cr.openjdk.org/~hannesw/8334241/api.00/java.base/java/lang/Object.html).

-------------

Commit messages:
 - JDK-8334241: Adjust API docs side bar dimensions

Changes: https://git.openjdk.org/jdk/pull/19726/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19726&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8334241
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/19726.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19726/head:pull/19726

PR: https://git.openjdk.org/jdk/pull/19726