patch 9.0.1633: duplicate code for converting float to string

Problem:    Duplicate code for converting float to string.
Solution:   Use tv_get_string(). (closes #12521)
diff --git a/src/eval.c b/src/eval.c
index 89141bf..8660a25 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -570,8 +570,7 @@
 
 /*
  * Convert "tv" to a string.
- * When "convert" is TRUE convert a List into a sequence of lines and convert
- * a Float to a String.
+ * When "convert" is TRUE convert a List into a sequence of lines.
  * Returns an allocated string (NULL when out of memory).
  */
     char_u *
@@ -579,7 +578,6 @@
 {
     garray_T	ga;
     char_u	*retval;
-    char_u	numbuf[NUMBUFLEN];
 
     if (convert && tv->v_type == VAR_LIST)
     {
@@ -593,11 +591,6 @@
 	ga_append(&ga, NUL);
 	retval = (char_u *)ga.ga_data;
     }
-    else if (convert && tv->v_type == VAR_FLOAT)
-    {
-	vim_snprintf((char *)numbuf, NUMBUFLEN, "%g", tv->vval.v_float);
-	retval = vim_strsave(numbuf);
-    }
     else
 	retval = vim_strsave(tv_get_string(tv));
     return retval;
@@ -606,8 +599,7 @@
 /*
  * Top level evaluation function, returning a string.  Does not handle line
  * breaks.
- * When "convert" is TRUE convert a List into a sequence of lines and convert
- * a Float to a String.
+ * When "convert" is TRUE convert a List into a sequence of lines.
  * Return pointer to allocated memory, or NULL for failure.
  */
     char_u *