records: don't replace `%` and `\` in table name if using `url_for`

[GraemeWatt]

For the new record ins3108682 with complex tables names like Figure 3a t(e) CR merged $U \in [250, 350] GeV$ bin, I noticed that the JSON button on the table record (https://www.hepdata.net/record/172708) returns an error "A data submission with record ID 167738, version 1 and table name 'Figure 3a t(e) CR merged bin' does not exist". Similarly if copying the URL for the table to the clipboard and appending &format=json. I think the reason is due to the replacement replace('\\', '%5C') in the lines:

hepdata/hepdata/modules/records/views.py

Line 111 in 77dc140

table_name=request.args['table'].replace('%', '%25').replace('\\', '%5C'),

hepdata/hepdata/modules/records/api.py

Line 452 in 77dc140

table_name = request.args['table'].replace('%', '%25').replace('\\', '%5C')

hepdata/hepdata/modules/records/api.py

Line 508 in 77dc140

table_name=ctx['table_name'].replace('%', '%25').replace('\\', '%5C'),

Testing locally, the JSON links work after removing the replacement. I think the replacement is no longer needed after simplifying the redirect with Flask url_for in commit 5793558 made last August. This should be tested more thoroughly before committing.