Bump buildbot to v3.11.7 release

Bump buildbot to v3.11.7 release

Changes since current v3.11.1 release:

 ### Bug Fixes
 - Fixed `GitPoller` when `repourl` has the port specified (:issue:`7822`).
 - Fixed `ChoiceStringParameter` fields with `multiple` would not store the selected values.
 - Fixed unnecessary trimming of spaces in logs shown in the web UI (:issue:`7774`).
 - Fixed favicon colors on build views in the web UI.
 - Fixed the icon on the about page in the web UI.
 - Fixed a regression where builds in waterfall view were no longer linking to the build page.
 - Transfer build steps (:bb:step:`FileUpload`, :bb:step:`DirectoryUpload`, :bb:step:`MultipleFileUpload`, :bb:step:`FileDownload`, and :bb:step:`StringDownload`) now correctly remove the destination on failure, preventing partial content (:issue:`2860`).
 - Fixed ReactUI when Buildbot is hosted behind a reverse proxy not at the URL's root (:issue:`7260`, :issue:`7746`).
 - Fixed results color shown on the builder's header in the waterfall view.
 - Fixed cases where the waterfall view could be squashed to a pixel high.
 - Fixed several occasional data update glitches in the web frontend.
 - Fixed the display of newly added builds in the Workers view in the web frontend.
 - Fixed a regression where `GitPoller` would no longer register new changes (regression introduced in 3.11.3 in #7554).
 - Fixed a bug that caused `GitPoller` running with git configured with the `fetch.prune=true` parameter to fail.
 - Fixed a bug that caused `GitPoller` to miss changes when Buildbot is reconfigured.
 - Reduced the length of directory names produced by `GitPoller` internally to avoid potential breakage on filesystems with low path and name length limits.
 - Removed credentials from `repourl` used in the tracker branch name.
 - Fixed an error in `HgPoller` when repository initialization fails (:issue:`7488`).
 - Updated the `Makefile` to handle Windows paths and Python.
 - Fixed the steps raw log download button.
 - Fixed a regression in the React UI that prevented hosting Buildbot at a custom URL prefix, allowing support for multiple Buildbot instances on a single server.

 ### Changes
 - Buildbot will now raise an error when configured with multiple services of the same type and name (:issue:`6987`).
 - Improved the flexibility of the `scaling_waterfall` setting to support floating-point values for a more condensed view.
 - Added a web configuration setting to select whether build completion or start times are displayed.
 - Added a revision info column in the web frontend.

 ### Features
 - Added `MessageFormatterFunctionRaw`, allowing complete customization of emitted messages. This feature has been available since 3.11.0 but was only recently announced.

 ### Deprecations and Removals
 - The `pollinterval` argument of various change sources has been deprecated with a warning in favor of `pollInterval`.

 ### Improved Documentation
 - Documented that `ChangeSource` does not support secrets (or any other renderables) and provided best practices for handling secret values in changes. Up until Buildbot 3.7, `ChangeSource` accidentally supported renderable arguments, which was undocumented behavior.

Signed-off-by: Petr Štetiar <ynezz@true.cz>