test: fix luacheck warnings in test/sql-tap (W231)

W231 (Local variable is set but never accessed)

Part of #5464

.luacheckrc

@@ -57,8 +57,6 @@ files["test/sql-tap/**/*.lua"] = {
     ignore = {
         -- Accessing an undefined global variable.
         "113",
-        -- Local variable is set but never accessed.
-        "231",
         -- "Value assigned to a local variable is unused."
         "311",
         -- Unreachable code.

test/sql-tap/e_expr.test.lua

@@ -2488,9 +2488,6 @@ test:do_execsql_test(
     })
 
 local a, b, c
-a = 0
-b = 0
-c = 0
 local varlist = {  }
 local function var(nm)
     table.insert(varlist,nm)
@@ -2555,9 +2552,6 @@ test:do_test(
 -- evaluation of the THEN expression that corresponds to the first WHEN
 -- expression that evaluates to true.
 --
-a = 0
-b = 1
-c = 0
 test:do_execsql_test(
     "e_expr-21.2.1",
     [[
@@ -2571,9 +2565,6 @@ test:do_execsql_test(
         "B"
         -- </e_expr-21.2.1>
     })
-a = 0
-b = 1
-c = 1
 test:do_execsql_test(
     "e_expr-21.2.2",
     [[
@@ -2587,9 +2578,6 @@ test:do_execsql_test(
         "B"
         -- </e_expr-21.2.2>
     })
-a = 0
-b = 0
-c = 1
 test:do_execsql_test(
     "e_expr-21.2.3",
     [[
@@ -2608,9 +2596,6 @@ test:do_execsql_test(
 -- evaluate to true, the result of evaluating the ELSE expression, if
 -- any.
 --
-a = 0
-b = 0
-c = 0
 test:do_execsql_test(
     "e_expr-21.3.1",
     [[
@@ -2847,9 +2832,6 @@ test:do_execsql_test(
 -- or short-circuit, evaluation.
 --
 varlist = {}
-a = "0"
-b = "1"
-c = "0"
 test:do_execsql_test(
     "e_expr-25.1.1",
     [[

test/sql-tap/func.test.lua

@@ -1359,7 +1359,6 @@ test:do_execsql_test(
         -- </13.8.4>
     })
 
-V = "two"
 test:do_execsql_test(
     "13.8.5",
     [[
@@ -1371,7 +1370,6 @@ test:do_execsql_test(
     })
 
 db("cache", "flush")
-V = "three"
 test:do_execsql_test(
     "13.8.6",
     [[