chore(deps): bump skyfield from 1.37 to 1.39

Bumps [skyfield](https://github.com/brandon-rhodes/python-skyfield) from 1.37 to 1.39.
- [Release notes](https://github.com/brandon-rhodes/python-skyfield/releases)
- [Changelog](https://github.com/skyfielders/python-skyfield/blob/master/CHANGELOG.rst)
- [Commits](https://github.com/brandon-rhodes/python-skyfield/compare/1.37...1.39)

Signed-off-by: dependabot[bot] <support@github.com>

Pipfile.lock

@@ -109,10 +109,10 @@
         },
         "skyfield": {
             "hashes": [
-                "sha256:64d2716187b94ccb587ec6db46ecb252fb14ecc3b32ef37ce6e90683bb5956cb"
+                "sha256:5a8da9720b49981bc6fc60ab8d52ef42a8d46fe7161e34ef6dd1d496de9903e2"
             ],
             "index": "pypi",
-            "version": "==1.37"
+            "version": "==1.39"
         },
         "tabulate": {
             "hashes": [
@@ -133,10 +133,10 @@
     "develop": {
         "astroid": {
             "hashes": [
-                "sha256:6b0ed1af831570e500e2437625979eaa3b36011f66ddfc4ce930128610258ca9",
-                "sha256:cd80bf957c49765dce6d92c43163ff9d2abc43132ce64d4b1b47717c6d2522df"
+                "sha256:ad63b8552c70939568966811a088ef0bc880f99a24a00834abd0e3681b514f91",
+                "sha256:bea3f32799fbb8581f58431c12591bc20ce11cbc90ad82e2ea5717d94f2080d5"
             ],
-            "version": "==2.5.2"
+            "version": "==2.5.3"
         },
         "babel": {
             "hashes": [
@@ -329,7 +329,6 @@
                 "sha256:2f4da4594db7e1e110a944bb1b551fdf4e6c136ad42e4234131391e21eb5b0df",
                 "sha256:e7b021f7241115872f92f43c6508082facffbd1c048e3c6e2bb9c2a157e28937"
             ],
-            "index": "pypi",
             "version": "==1.26.4"
         },
         "wrapt": {