Pass --context option to "before" lines of inline diffs

Perhaps, this was just an oversight.

BTW, inline diffs print one more context lines than specified, which I'll fix
separately.

src/display/inline.rs

@@ -75,8 +75,12 @@ pub(crate) fn print(
 
         let hunk_lines = &hunk.lines;
 
-        let before_lines =
-            calculate_before_context(hunk_lines, &opposite_to_lhs, &opposite_to_rhs, 3);
+        let before_lines = calculate_before_context(
+            hunk_lines,
+            &opposite_to_lhs,
+            &opposite_to_rhs,
+            display_options.num_context_lines as usize,
+        );
         let after_lines = calculate_after_context(
             &[&before_lines[..], &hunk_lines[..]].concat(),
             &opposite_to_lhs,