make random choice of example proteins constant for each session

ProtHGT_app.py

@@ -38,6 +38,8 @@ if 'submitted' not in st.session_state:
     st.session_state.submitted = False
 if 'previous_inputs' not in st.session_state:
     st.session_state.previous_inputs = None
+if 'example_proteins' not in st.session_state:
+    st.session_state.example_proteins = random.sample(available_proteins, 5)
 
 with st.expander("🚀 Upcoming Features"):
     st.info("""
@@ -91,7 +93,6 @@ with st.sidebar:
     )
 
     if selection_method == "Use example query":
-        st.session_state.example_proteins = random.sample(available_proteins, 5)
         selected_proteins = st.session_state.example_proteins
 
     elif selection_method == "Search proteins":