chore: pin setuptools_scm [backport 1.19] (#7008)

Backport bc10daf from #7005 to 1.19.

This change pins setuptools_scm below version 8, which dropped support
for Python versions <=3.6.

## Checklist

- [x] Change(s) are motivated and described in the PR description.
- [x] Testing strategy is described if automated tests are not included
in the PR.
- [x] Risk is outlined (performance impact, potential for breakage,
maintainability, etc).
- [x] Change is maintainable (easy to change, telemetry, documentation).
- [x] [Library release note
guidelines](https://ddtrace.readthedocs.io/en/stable/releasenotes.html)
are followed. If no release note is required, add label
`changelog/no-changelog`.
- [x] Documentation is included (in-code, generated user docs, [public
corp docs](https://github.com/DataDog/documentation/)).
- [x] Backport labels are set (if
[applicable](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting))

## Reviewer Checklist

- [x] Title is accurate.
- [x] No unnecessary changes are introduced.
- [x] Description motivates each change.
- [x] Avoids breaking
[API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces)
changes unless absolutely necessary.
- [x] Testing strategy adequately addresses listed risk(s).
- [x] Change is maintainable (easy to change, telemetry, documentation).
- [x] Release note makes sense to a user of the library.
- [x] Reviewer has explicitly acknowledged and discussed the performance
implications of this PR as reported in the benchmarks PR comment.
- [x] Backport labels are set in a manner that is consistent with the
[release branch maintenance
policy](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting)
- [x] If this PR touches code that signs or publishes builds or
packages, or handles credentials of any kind, I've requested a review
from `@DataDog/security-design-and-guidance`.
- [x] This PR doesn't touch any of that.

Co-authored-by: Emmett Butler <[email protected]>

Author: github-actions[bot]

pyproject.toml

@@ -1,5 +1,5 @@
 [build-system]
-requires = ["setuptools_scm[toml]>=4", "cython<3", "cmake>=3.24.2; python_version>='3.6'"]
+requires = ["setuptools_scm[toml]>=4,<8", "cython<3", "cmake>=3.24.2; python_version>='3.6'"]
 build-backend = "setuptools.build_meta"
 
 [project]

setup.py

@@ -6,7 +6,6 @@
 import sys
 import tarfile
 
-
 from setuptools import Extension, find_packages, setup  # isort: skip
 from setuptools.command.build_ext import build_ext  # isort: skip
 from setuptools.command.build_py import build_py as BuildPyCommand  # isort: skip
@@ -17,8 +16,8 @@
 try:
     # ORDER MATTERS
     # Import this after setuptools or it will fail
-    from Cython.Build import cythonize  # noqa: I100
     import Cython.Distutils
+    from Cython.Build import cythonize  # noqa: I100
 except ImportError:
     raise ImportError(
         "Failed to import Cython modules. This can happen under versions of pip older than 18 that don't "
@@ -594,7 +593,7 @@ def get_ddup_ext():
         "Programming Language :: Python :: 3.10",
         "Programming Language :: Python :: 3.11",
     ],
-    setup_requires=["setuptools_scm[toml]>=4", "cython<3", "cmake>=3.24.2; python_version>='3.6'"],
+    setup_requires=["setuptools_scm[toml]>=4,<8", "cython<3", "cmake>=3.24.2; python_version>='3.6'"],
     ext_modules=ext_modules
     + cythonize(
         [