Fix lineCount description: count is exact, not approximate

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: cmdcolin

README.md

@@ -257,7 +257,7 @@ line that overlaps the given region
 
 #### lineCount
 
-return the approximate number of data lines in the given reference sequence
+return the number of data lines in the given reference sequence
 
 ##### Parameters
 

src/tabixIndexedFile.ts

@@ -429,7 +429,7 @@ export default class TabixIndexedFile {
   }
 
   /**
-   * return the approximate number of data lines in the given reference sequence
+   * return the number of data lines in the given reference sequence
    * @param {string} refName reference sequence name
    * @returns {number} number of data lines present on that reference sequence
    */