gh-38667: Fix pyproject.toml use of inline tables
    
Make project.urls a standard table so we can use line breaks

Caused by #38577

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URL: #38667
Reported by: Volker Braun
Reviewer(s): David Coudert, Dima Pasechnik

Author: Release Manager

m4/pyproject_toml_metadata.m4

@@ -17,10 +17,12 @@ classifiers = [
     "Programming Language :: Python :: Implementation :: CPython",
     "Topic :: Scientific/Engineering :: Mathematics",
 ]
-urls = {download = "https://doc.sagemath.org/html/en/installation/index.html",
-        "release notes" = "https://github.com/sagemath/sage/releases",
-        source = "https://github.com/sagemath/sage",
-        documentation = "https://doc.sagemath.org",
-        homepage = "https://www.sagemath.org",
-        tracker = "https://github.com/sagemath/sage/issues"}
 requires-python = ">=3.9, <3.13"
+
+[project.urls]
+download = "https://doc.sagemath.org/html/en/installation/index.html"
+"release notes" = "https://github.com/sagemath/sage/releases"
+source = "https://github.com/sagemath/sage"
+documentation = "https://doc.sagemath.org"
+homepage = "https://www.sagemath.org"
+tracker = "https://github.com/sagemath/sage/issues"