Fix order in requirements-swh-dev.txt

swh-web depends on swh-indexer so we must ensure swh-indexer is installed
first (otherwise the last pubished version is used instead of the one
from the sources).

requirements-swh-dev.txt

@@ -16,7 +16,7 @@
 ../swh-loader-svn
 ../swh-loader-git
 ../swh-archiver
+../swh-indexer
 ../swh-web
 ../swh-deposit
-../swh-indexer
 ../swh-mirror-forge