Update pandas to 1.3.4 (#641)

* Update pandas from 1.3.3 to 1.3.4
diff --git a/extra_requirements.txt b/extra_requirements.txt
index 024e1fd..0d5dc1c 100644
--- a/extra_requirements.txt
+++ b/extra_requirements.txt
@@ -14,6 +14,6 @@
 # pyfakefs to work with pandas
 # we use the latest version to see any problems with new versions
 pandas==1.1.5; python_version <= '3.6'
-pandas==1.3.3; python_version > '3.6'
+pandas==1.3.4; python_version > '3.6'
 xlrd==1.2.0
 openpyxl==3.0.9