[web] Remove extraneous display: inline-block in calendar.css

Summary:
Saw a CSS warning that the display: inline-block was ignored due to the float: right property:

Test Plan:
Tested to make sure the Entry (where this rule is applied) in the Calendar looked as expected.

Before:

Reviewers: atul, palys-swm

Reviewed By: palys-swm

Subscribers: ashoat, Adrian

Differential Revision: https://phab.comm.dev/D4344