update pathway in .flake8

Author: cadenmyers13

.flake8

@@ -6,7 +6,7 @@ exclude =
     dist,
     versioneer.py,
     labpdfproc/_version.py,
-    docs/source/conf.py
+    doc/manual/source/conf.py
 max-line-length = 115
 # Ignore some style 'errors' produced while formatting by 'black'
 ignore = E203, W503