Fix dates in changelog (2020 -> 2021).

Author: jonathanslenders

CHANGELOG

@@ -1,7 +1,8 @@
 CHANGELOG
 =========
 
-3.0.19: 2020-07-08
+
+3.0.19: 2021-07-08
 ------------------
 
 Fixes:
@@ -10,14 +11,14 @@ Fixes:
 - Allow usage of `await` in assignment expressions or for-loops.
 
 
-3.0.18: 2020-06-26
+3.0.18: 2021-06-26
 ------------------
 
 Fixes:
 - Made "black" an optional dependency.
 
 
-3.0.17: 2020-03-22
+3.0.17: 2021-03-22
 ------------------
 
 Fixes:
@@ -26,7 +27,7 @@ Fixes:
 - Fix race condition during retrieval of signatures.
 
 
-3.0.16: 2020-02-11
+3.0.16: 2021-02-11
 ------------------
 
 (Commit 7f619e was missing in previous release.)
@@ -38,7 +39,7 @@ Fixes:
     completions were missed out if the fuzzy completer doesn't find them.
 
 
-3.0.15: 2020-02-11
+3.0.15: 2021-02-11
 ------------------
 
 New features:
@@ -48,7 +49,7 @@ Fixes:
 - Fix `AttributeError` during retrieval of signatures with type annotations.
 
 
-3.0.14: 2020-02-10
+3.0.14: 2021-02-10
 ------------------
 
 New features:
@@ -67,7 +68,7 @@ Fixes:
 - Hide signature when sidebar is visible.
 
 
-3.0.13: 2020-01-26
+3.0.13: 2021-01-26
 ------------------
 
 New features:
@@ -82,7 +83,7 @@ Fixes:
 - Fix line ending bug in pager.
 
 
-3.0.12: 2020-01-24
+3.0.12: 2021-01-24
 ------------------
 
 New features:
@@ -96,7 +97,7 @@ Fixes:
 - Properly handle `SystemExit`.
 
 
-3.0.11: 2020-01-20
+3.0.11: 2021-01-20
 ------------------
 
 New features:
@@ -119,7 +120,7 @@ Fixes:
 - Don't execute PYTHONSTARTUP when -i flag was given.
 
 
-3.0.10: 2020-01-13
+3.0.10: 2021-01-13
 ------------------
 
 Fixes:
@@ -128,7 +129,7 @@ Fixes:
   default.
 
 
-3.0.9: 2020-01-10
+3.0.9: 2021-01-10
 -----------------
 
 New features:
@@ -137,7 +138,7 @@ New features:
 - Show REPL title in pager.
 
 
-3.0.8: 2020-01-05
+3.0.8: 2021-01-05
 -----------------
 
 New features: