Bump libmongoc and libmongocrypt versions for system library testing

Author: jmikola

.github/workflows/tests.yml

@@ -134,8 +134,8 @@ jobs:
     runs-on: "ubuntu-latest"
     env:
       PHP_VERSION: "8.3"
-      LIBMONGOCRYPT_VERSION: "1.14"
-      LIBMONGOC_VERSION: "2.0.2"
+      LIBMONGOCRYPT_VERSION: "1.15.2"
+      LIBMONGOC_VERSION: "2.1.0"
       SERVER_VERSION: "8.0"
 
     steps:

CONTRIBUTING.md

@@ -272,6 +272,12 @@ against two additional versions of libmongoc:
   `r2.x` branch)
 - The upcoming minor release of libmongoc (e.g. the `master` branch)
 
+#### Update tested system library versions in GitHub Actions
+
+GitHub Actions tests against libmongoc and libmongocrypt system libraries. When
+updating the version number for each dependency in `config.m4` you must also
+update environment variables for the `test-system-libs` job in `tests.yml`.
+
 #### Update sources in PECL package generation script
 
 If a new version of a submodule introduces a new source directory, that may also