Rename `s` to `source`

spec/ameba/rule/layout/trailing_blank_lines_spec.cr

@@ -13,18 +13,18 @@ module Ameba::Rule::Layout
     end
 
     it "fails if there is no blank lines at the end" do
-      s = expect_issue subject, "no-blankline # error: Trailing newline missing"
-      expect_correction s, "no-blankline\n"
+      source = expect_issue subject, "no-blankline # error: Trailing newline missing"
+      expect_correction source, "no-blankline\n"
     end
 
     it "fails if there more then one blank line at the end of a source" do
-      s = expect_issue subject, "a = 1\n \n # error: Excessive trailing newline detected", normalize: false
-      expect_no_corrections s
+      source = expect_issue subject, "a = 1\n \n # error: Excessive trailing newline detected", normalize: false
+      expect_no_corrections source
     end
 
     it "fails if last line is not blank" do
-      s = expect_issue subject, "\n\n\n puts 22 # error: Trailing newline missing", normalize: false
-      expect_correction s, "\n\n\n puts 22\n"
+      source = expect_issue subject, "\n\n\n puts 22 # error: Trailing newline missing", normalize: false
+      expect_correction source, "\n\n\n puts 22\n"
     end
 
     context "when unnecessary blank line has been detected" do

spec/ameba/rule/style/large_numbers_spec.cr

@@ -7,12 +7,12 @@ module Ameba
     it "transforms large number #{number}" do
       rule = Rule::Style::LargeNumbers.new
 
-      s = expect_issue rule, <<-CRYSTAL, number: number
+      source = expect_issue rule, <<-CRYSTAL, number: number
         number = %{number}
                # ^{number} error: Large numbers should be written with underscores: #{expected}
         CRYSTAL
 
-      expect_correction s, <<-CRYSTAL
+      expect_correction source, <<-CRYSTAL
         number = #{expected}
         CRYSTAL
     end