patch 8.2.5029: "textlock" is always zero

Problem:    "textlock" is always zero.
Solution:   Remove "textlock" and rename "textwinlock" to "textlock".
            (closes #10489)
diff --git a/src/beval.c b/src/beval.c
index a9d10a2..4b89af3 100644
--- a/src/beval.c
+++ b/src/beval.c
@@ -284,7 +284,7 @@
 	    curbuf = save_curbuf;
 	    if (use_sandbox)
 		++sandbox;
-	    ++textwinlock;
+	    ++textlock;
 
 	    if (bexpr == p_bexpr)
 	    {
@@ -311,7 +311,7 @@
 
 	    if (use_sandbox)
 		--sandbox;
-	    --textwinlock;
+	    --textlock;
 	    current_sctx = save_sctx;
 
 	    set_vim_var_string(VV_BEVAL_TEXT, NULL, -1);