patch 8.2.0967: unnecessary type casts for vim_strnsave()

Problem:    Unnecessary type casts for vim_strnsave().
Solution:   Remove the type casts.
diff --git a/src/vim9compile.c b/src/vim9compile.c
index f59ec12..17c16d8 100644
--- a/src/vim9compile.c
+++ b/src/vim9compile.c
@@ -1575,7 +1575,7 @@
     RETURN_OK_IF_SKIP(cctx);
     if ((isn = generate_instr(cctx, ISN_STRINGMEMBER)) == NULL)
 	return FAIL;
-    isn->isn_arg.string = vim_strnsave(name, (int)len);
+    isn->isn_arg.string = vim_strnsave(name, len);
 
     // check for dict type
     type = ((type_T **)stack->ga_data)[stack->ga_len - 1];
@@ -1671,7 +1671,7 @@
     // entries.  This is less efficient, but memory is cheap these days.
     lvar->lv_idx = cctx->ctx_locals_count++;
 
-    lvar->lv_name = vim_strnsave(name, (int)(len == 0 ? STRLEN(name) : len));
+    lvar->lv_name = vim_strnsave(name, len == 0 ? STRLEN(name) : len);
     lvar->lv_const = isConst;
     lvar->lv_type = type;
 
@@ -4627,7 +4627,7 @@
 	--p;
 
     varlen = p - arg;
-    name = vim_strnsave(arg, (int)varlen);
+    name = vim_strnsave(arg, varlen);
     if (name == NULL)
 	return NULL;
 
@@ -6268,7 +6268,7 @@
 	{
 	    if (p > start)
 	    {
-		generate_PUSHS(cctx, vim_strnsave(start, (int)(p - start)));
+		generate_PUSHS(cctx, vim_strnsave(start, p - start));
 		++count;
 	    }
 	    p += 2;