Don't build wheels for Python 3.7 (#15917)

* Don't build wheels for CPython or PyPy 3.7

* Update pyproject.toml comments

* Manually update the changelog

Author: David Robertson

CHANGES.md

@@ -24,7 +24,7 @@ See [the upgrade notes](https://github.com/matrix-org/synapse/blob/release-v1.88
 ### Deprecations and Removals
 
 - **Remove deprecated `worker_replication_host`, `worker_replication_http_port` and `worker_replication_http_tls` configuration options.** See the [upgrade notes](https://github.com/matrix-org/synapse/blob/release-v1.88/docs/upgrade.md#removal-of-worker_replication_-settings) for more details. ([\#15860](https://github.com/matrix-org/synapse/issues/15860))
-- Remove support for Python 3.7 and hence for Debian Buster. ([\#15851](https://github.com/matrix-org/synapse/issues/15851), [\#15892](https://github.com/matrix-org/synapse/issues/15892), [\#15893](https://github.com/matrix-org/synapse/issues/15893))
+- Remove support for Python 3.7 and hence for Debian Buster. ([\#15851](https://github.com/matrix-org/synapse/issues/15851), [\#15892](https://github.com/matrix-org/synapse/issues/15892), [\#15893](https://github.com/matrix-org/synapse/issues/15893), [\#15917](https://github.com/matrix-org/synapse/pull/15917))
 
 ### Internal Changes
 

pyproject.toml

@@ -373,7 +373,15 @@ build-backend = "poetry.core.masonry.api"
 
 [tool.cibuildwheel]
 # Skip unsupported platforms (by us or by Rust).
-skip = "cp36* *-musllinux_i686 pp*aarch64 *-musllinux_aarch64"
+# See https://cibuildwheel.readthedocs.io/en/stable/options/#build-skip for the list of build targets.
+# We skip:
+#  - CPython 3.6 and 3.7: EOLed
+#  - PyPy 3.7: we only support Python 3.8+
+#  - musllinux i686: excluded to reduce number of wheels we build.
+#    c.f. https://github.com/matrix-org/synapse/pull/12595#discussion_r963107677
+#  - PyPy on Aarch64 and musllinux on aarch64: too slow to build.
+#    c.f. https://github.com/matrix-org/synapse/pull/14259
+skip = "cp36* cp37* pp37* *-musllinux_i686 pp*aarch64 *-musllinux_aarch64"
 
 # We need a rust compiler
 before-all =  "curl https://sh.rustup.rs -sSf | sh -s -- --default-toolchain stable -y --profile minimal"