[ruby/syntax_suggest] Clean up output

I previously left a comment stating I didn't know why a certain method existed. In investigating the code in `CaptureCodeContext#capture_before_after_kws` I found that it was added as to give a slightly less noisy output.

The docs for AroundBlockScan#capture_neighbor_context only describe keywords as being a primary concern. I modified that code to only include lines that are keywords or ends. This reduces the output noise even more.

This allows me to remove that `start_at_next_line` method.

One weird side effect of the prior logic is it would cause this code to produce this output:

```
        class OH
          def hello

          def hai
          end
        end
```

```
          1  class OH
        > 2    def hello
          4    def hai
          5    end
          6  end
```

But this code to produce this output:

```
        class OH
          def hello
          def hai
          end
        end
```

```
          1  class OH
        > 2    def hello
          4    end
          5  end
```
Note the missing `def hai`. The only difference between them is that space.

With this change, they're now both consistent.

https://github.com/ruby/syntax_suggest/commit/4a54767a3e

2 files changed, 2 insertions, 21 deletions

diff --git a/lib/syntax_suggest/around_block_scan.rb b/lib/syntax_suggest/around_block_scan.rb
index 656246c0af..fe63470dee 100644
--- a/lib/syntax_suggest/around_block_scan.rb
+++ b/lib/syntax_suggest/around_block_scan.rb
@@ -176,7 +176,7 @@ module SyntaxSuggest
           break
         end
 
-        lines << line
+        lines << line if line.is_kw? || line.is_end?
       end
 
       lines.reverse!
@@ -195,7 +195,7 @@ module SyntaxSuggest
           break
         end
 
-        lines << line
+        lines << line if line.is_kw? || line.is_end?
       end
 
       lines
@@ -319,24 +319,6 @@ module SyntaxSuggest
       self
     end
 
-    # TODO: Doc or delete
-    #
-    # I don't remember why this is needed, but it's called in code_context.
-    # It's related to the implementation of `capture_neighbor_context` somehow
-    # and that display improvement is only triggered when there's one visible line
-    #
-    # I think the primary purpose is to not include the current line in the
-    # logic evaluation of `capture_neighbor_context`. If that's true, then
-    # we should fix that method to handle this logic instead of only using
-    # it in one place and together.
-    def start_at_next_line
-      before_index
-      after_index
-      @before_index -= 1
-      @after_index += 1
-      self
-    end
-
     # Return the currently matched lines as a `CodeBlock`
     #
     # When a `CodeBlock` is created it will gather metadata about
diff --git a/lib/syntax_suggest/capture_code_context.rb b/lib/syntax_suggest/capture_code_context.rb
index 547072e2bd..a618b2ec68 100644
--- a/lib/syntax_suggest/capture_code_context.rb
+++ b/lib/syntax_suggest/capture_code_context.rb
@@ -116,7 +116,6 @@ module SyntaxSuggest
       return unless block.visible_lines.count == 1
 
       around_lines = AroundBlockScan.new(code_lines: @code_lines, block: block)
-        .start_at_next_line
         .capture_neighbor_context
 
       around_lines -= block.lines