test_linkcheck_allowed_redirects: reduce the number of HTTP round-tri…

…ps by enabling support for HEAD requests

This is intended to reduce the number of HTTP requests within this particular test to closer-to-the-norm compared to other tests within the test_build_linkcheck.py module; this test has been failing intermittently and it seems possible that timeouts due to HTTP roundtrip traffic are a contributing factor.

(cherry picked from commit c2d5bef)

tests/test_build_linkcheck.py

@@ -419,7 +419,7 @@ def test_follows_redirects_on_GET(app, capsys, warning):
                         'linkcheck_allowed_redirects': {'http://localhost:7777/.*1': '.*'},
                     })
 def test_linkcheck_allowed_redirects(app, warning):
-    with http_server(make_redirect_handler(support_head=False)):
+    with http_server(make_redirect_handler(support_head=True)):
         app.build()
 
     with open(app.outdir / 'output.json', encoding='utf-8') as fp: