src/sage/graphs: move is_projective_planar() tests to a subdirectory

A simple `git mv` with an update of the associated meson.build files.

Author: orlitzky

src/sage/graphs/meson.build

@@ -67,7 +67,6 @@ py.install_sources(
   'independent_sets.pyx',
   'isgci.py',
   'isoperimetric_inequalities.pyx',
-  'is_projective_planar_test.py',
   'line_graph.pyx',
   'lovasz_theta.py',
   'matching.py',
@@ -92,6 +91,7 @@ py.install_sources(
   subdir: 'sage/graphs',
 )
 
+
 extension_data = {
   'asteroidal_triples' : files('asteroidal_triples.pyx'),
   'centrality' : files('centrality.pyx'),
@@ -179,3 +179,4 @@ py.extension_module(
 subdir('base')
 subdir('generators')
 subdir('graph_decompositions')
+subdir('tests')

src/sage/graphs/is_projective_planar_test.py renamed to src/sage/graphs/tests/is_projective_planar_test.py

@@ -0,0 +1,5 @@
+py.install_sources(
+  '__init__.py',
+  'is_projective_planar_test.py',
+  subdir: 'sage/graphs/tests',
+)