Remove unnecessary email converter

The homework and exam grades don't have an Email Address column, so the
converter isn't necessary

pandas-gradebook-project/01-loading-the-data.py

@@ -27,7 +27,7 @@ roster = pd.read_csv(
 
 hw_exam_grades = pd.read_csv(
     DATA_FOLDER / "hw_exam_grades.csv",
-    converters={"SID": str.lower, "Email Address": str.lower},
+    converters={"SID": str.lower},
     usecols=lambda x: "Submission" not in x,
     index_col="SID",
 )

pandas-gradebook-project/02-merging-dataframes.py

@@ -27,7 +27,7 @@ roster = pd.read_csv(
 
 hw_exam_grades = pd.read_csv(
     DATA_FOLDER / "hw_exam_grades.csv",
-    converters={"SID": str.lower, "Email Address": str.lower},
+    converters={"SID": str.lower},
     usecols=lambda x: "Submission" not in x,
     index_col="SID",
 )

pandas-gradebook-project/03-calculating-grades.py

@@ -28,7 +28,7 @@ roster = pd.read_csv(
 
 hw_exam_grades = pd.read_csv(
     DATA_FOLDER / "hw_exam_grades.csv",
-    converters={"SID": str.lower, "Email Address": str.lower},
+    converters={"SID": str.lower},
     usecols=lambda x: "Submission" not in x,
     index_col="SID",
 )

pandas-gradebook-project/04-grouping-the-data.py

@@ -28,7 +28,7 @@ roster = pd.read_csv(
 
 hw_exam_grades = pd.read_csv(
     DATA_FOLDER / "hw_exam_grades.csv",
-    converters={"SID": str.lower, "Email Address": str.lower},
+    converters={"SID": str.lower},
     usecols=lambda x: "Submission" not in x,
     index_col="SID",
 )

pandas-gradebook-project/05-plotting-summary-statistics.py

@@ -30,7 +30,7 @@ roster = pd.read_csv(
 
 hw_exam_grades = pd.read_csv(
     DATA_FOLDER / "hw_exam_grades.csv",
-    converters={"SID": str.lower, "Email Address": str.lower},
+    converters={"SID": str.lower},
     usecols=lambda x: "Submission" not in x,
     index_col="SID",
 )

pandas-gradebook-project/06-final-gradebook.py

@@ -26,7 +26,7 @@ roster = pd.read_csv(
 
 hw_exam_grades = pd.read_csv(
     DATA_FOLDER / "hw_exam_grades.csv",
-    converters={"SID": str.lower, "Email Address": str.lower},
+    converters={"SID": str.lower},
     usecols=lambda x: "Submission" not in x,
     index_col="SID",
 )