[libpqxx] Update to version 7.9.0 (#36993)

Fixes #36968, updating `libpqxx` to 7.9.0.

No feature needs to be tested.

- [x] Changes comply with the [maintainer
guide](https://github.com/microsoft/vcpkg-docs/blob/main/vcpkg/contributing/maintainer-guide.md).
- [x] SHA512s are updated for each updated download.
- [ ] ~~The "supports" clause reflects platforms that may be fixed by
this new version.~~
- [ ] ~~Any fixed [CI
baseline](https://github.com/microsoft/vcpkg/blob/master/scripts/ci.baseline.txt)
entries are removed from that file.~~
- [ ] ~~Any patches that are no longer applied are deleted from the
port's directory.~~
- [x] The version database is fixed by rerunning `./vcpkg x-add-version
--all` and committing the result.
- [x] Only one version is added to each modified port's versions file.

---------

Co-authored-by: Sam Barrett <s.barrett@qed-analytics.co.uk>

ports/libpqxx/portfile.cmake

@@ -2,7 +2,7 @@ vcpkg_from_github(
     OUT_SOURCE_PATH SOURCE_PATH
     REPO jtv/libpqxx
     REF "${VERSION}"
-    SHA512 ce37fdfce2671d97e422ae3339fb5650065111b0635a7293200c56a8755a7dc7de80806816863c606c46b6049e4cb490d24dfb97446ea0014b55907554862fed
+    SHA512 134e28177f6a205c8a45462fa6b3cb4c407ab8f03a45708400fdc9f567d2ba1fae9cce9d541bdccd46694bf5d1b8dfd72bc6de5f6c915181909623357f86ce47
     HEAD_REF master
     PATCHES
         fix_build_with_vs2017.patch

ports/libpqxx/vcpkg.json

@@ -1,6 +1,6 @@
 {
   "name": "libpqxx",
-  "version": "7.8.1",
+  "version": "7.9.0",
   "description": "The official C++ client API for PostgreSQL",
   "homepage": "https://www.postgresql.org/",
   "license": "BSD-3-Clause",

versions/baseline.json

@@ -4753,7 +4753,7 @@
       "port-version": 0
     },
     "libpqxx": {
-      "baseline": "7.8.1",
+      "baseline": "7.9.0",
       "port-version": 0
     },
     "libprotobuf-mutator": {

versions/l-/libpqxx.json

@@ -1,5 +1,10 @@
 {
   "versions": [
+    {
+      "git-tree": "c8078815fcddf1da8e7d8fba66100befaa779ec0",
+      "version": "7.9.0",
+      "port-version": 0
+    },
     {
       "git-tree": "8083e94ed4ded4546cbad5263a7efb4b9b154b73",
       "version": "7.8.1",