Merge duplicate section in pyproject.toml

The build was stopping due to issues within the pyproject.toml,
which was specifying two times the section for optional
dependencies. The two conflicting sections are now merged
into one, and this should solve the issues.

Author: bastonero

pyproject.toml

@@ -23,11 +23,6 @@ dependencies = [
 # entries = { scripts = ["scripts/sscha", "scripts/cluster_check.x", ...] }
 # However, Meson is better at handling scripts like install_data
 
-[project.optional-dependencies]
-# Fast Julia-accelerated fourier gradients. juliacall installs the Julia
-# runtime automatically at first use, no further setup is required.
-julia = ["juliacall"]
-
 [project.scripts]
 sscha-plot-data="sscha.cli:plot_data"
 sscha="sscha.cli:main"
@@ -39,6 +34,9 @@ Repository = "https://github.com/SSCHAcode/python-sscha"
 Issues = "https://github.com/SSCHAcode/python-sscha/issues"
 
 [project.optional-dependencies]
+# Fast Julia-accelerated fourier gradients. juliacall installs the Julia
+# runtime automatically at first use, no further setup is required.
+julia = ["juliacall"]
 pre-commit = [
     'pre-commit~=2.17',
     'pylint==2.13.7',