Remove isolated data creation useless assignments

While there are other variables in these tests, they're not part of the
setup of the test, and so these ones can be removed while keeping the
code easy to read.

spec/lib/user_segments_spec.rb

@@ -51,7 +51,7 @@ describe UserSegments do
 
   describe "#proposal_authors" do
     it "returns users that have created a proposal" do
-      proposal = create(:proposal, author: user1)
+      create(:proposal, author: user1)
 
       proposal_authors = UserSegments.proposal_authors
       expect(proposal_authors).to include user1
@@ -59,8 +59,8 @@ describe UserSegments do
     end
 
     it "does not return duplicated users" do
-      proposal1 = create(:proposal, author: user1)
-      proposal2 = create(:proposal, author: user1)
+      create(:proposal, author: user1)
+      create(:proposal, author: user1)
 
       proposal_authors = UserSegments.proposal_authors
       expect(proposal_authors).to contain_exactly(user1)