Remove one-line methods

Unnecessary level of abstraction

spec/ameba/ast/util_spec.cr

@@ -36,16 +36,6 @@ module Ameba::AST
       end
     end
 
-    describe "#string_literal?" do
-      it "returns true if node is a string literal" do
-        subject.string_literal?(Crystal::StringLiteral.new "").should be_true
-      end
-
-      it "returns false if node is not a string literal" do
-        subject.string_literal?(Crystal::Nop.new).should be_false
-      end
-    end
-
     describe "#node_source" do
       it "returns original source of the node" do
         s = %(

src/ameba/ast/util.cr

@@ -27,16 +27,6 @@ module Ameba::AST::Util
     end
   end
 
-  # Returns true if current `node` is a string literal, false otherwise.
-  def string_literal?(node)
-    node.is_a? Crystal::StringLiteral
-  end
-
-  # Returns true if current `node` is an exception handler, false otherwise.
-  def exception_handler?(node)
-    node.is_a? Crystal::ExceptionHandler
-  end
-
   # Returns a source code for the current node.
   # This method uses `node.location` and `node.end_location`
   # to determine and cut a piece of source of the node.

src/ameba/rule/lint/literal_in_interpolation.cr

@@ -30,7 +30,7 @@ module Ameba::Rule::Lint
     end
 
     def test(source, node : Crystal::StringInterpolation)
-      found = node.expressions.any? { |e| !string_literal?(e) && literal?(e) }
+      found = node.expressions.any? { |e| !e.is_a?(Crystal::StringLiteral) && literal?(e) }
       return unless found
       issue_for node, MSG
     end

src/ameba/rule/style/redundant_begin.cr

@@ -102,7 +102,7 @@ module Ameba::Rule::Style
 
     private def begin_exprs_in_handler?(handler)
       if (body = handler.body).is_a?(Crystal::Expressions)
-        exception_handler?(body.expressions.first)
+        body.expressions.first.is_a?(Crystal::ExceptionHandler)
       end
     end