Fix find same course

[lithops-zty]

closes #246

Fix:

Let ModuleRoleContainsKeywordsPredicate use a 'Set' instead of ModuleRoleMap to bypass duplicate checking.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 84.00000% with 4 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...el/person/ModuleRoleContainsKeywordsPredicate.java	66.66%	3 Missing :warning:
...java/seedu/address/logic/commands/FindCommand.java	85.71%	0 Missing and 1 partial :warning:

Files with missing lines	Coverage Δ	Complexity Δ
...a/seedu/address/logic/parser/AddCommandParser.java	100.00% <100.00%> (ø)	9.00 <0.00> (ø)
.../seedu/address/logic/parser/FindCommandParser.java	90.00% <100.00%> (ø)	13.00 <0.00> (ø)
...in/java/seedu/address/logic/parser/ParserUtil.java	94.21% <100.00%> (+0.30%)	44.00 <3.00> (+2.00)
...java/seedu/address/logic/commands/FindCommand.java	92.85% <85.71%> (ø)	17.00 <3.00> (ø)
...el/person/ModuleRoleContainsKeywordsPredicate.java	82.35% <66.66%> (-17.65%)	7.00 <3.00> (-1.00)

... and 2 files with indirect coverage changes