Remove optional test dependencies we do not have packaged yet.

--- pyfakefs-5.7.1/extra_requirements.txt.orig
+++ pyfakefs-5.7.1/extra_requirements.txt
@@ -1,9 +0,0 @@
-# these are used to test pandas-specific patches to allow
-# pyfakefs to work with pandas
-# we use the latest version to see any problems with new versions
-pandas==1.3.5; python_version == '3.7' # pyup: ignore
-pandas==2.0.3; python_version == '3.8' # pyup: ignore
-pandas==2.2.3; python_version > '3.8'
-xlrd==2.0.1
-openpyxl==3.1.3; python_version == '3.7' # pyup: ignore
-openpyxl==3.1.5; python_version > '3.7'