Remove terminal colouring from test output so it is (#14810)

more readable in CI.

```
Running primary verification step for case-ingress-gateway-multiple-services...
�[34;1mverify.bats
�[0m�[1G   ingress proxy admin is up on :20000�[K�[75G 1/12�[2G�[1G ✓ ingress proxy admin is up on :20000�[K
�[0m�[1G   s1 proxy admin is up on :19000�[K�[75G 2/12�[2G�[1G ✓ s1 proxy admin is up on :19000�[K
�[0m�[1G   s2 proxy admin is up on :19001�[K�[75G 3/12�[2G�[1G ✓ s2 proxy admin is up on :19001�[K
�[0m�[1G   s1 proxy listener should be up and have right cert�[K�[75G 4/12�[2G�[1G ✓ s1 proxy listener should be up and have right cert�[K
�[0m�[1G   s2 proxy listener should be up and have right cert�[K�[75G 5/12�[2G�[1G ✓ s2 proxy listener should be up and have right cert�[K
�[0m�[1G   ingress-gateway should have healthy endpoints for s1�[K�[75G 6/12�[2G�[31;1m�[1G ✗ ingress-gateway should have healthy endpoints for s1�[K
�[0m�[31;22m   (from function `assert_upstream_has_endpoints_in_status' in file /workdir/primary/bats/helpers.bash, line 385,
```

versus

```
Running primary verification step for case-ingress-gateway-multiple-services...
1..12
ok 1 ingress proxy admin is up on :20000
ok 2 s1 proxy admin is up on :19000
ok 3 s2 proxy admin is up on :19001
ok 4 s1 proxy listener should be up and have right cert
ok 5 s2 proxy listener should be up and have right cert
not ok 6 ingress-gateway should have healthy endpoints for s1
not ok 7 s1 proxy should have been configured with max_connections in services
ok 8 ingress-gateway should have healthy endpoints for s2
```

test/integration/connect/envoy/helpers.bash

@@ -51,34 +51,6 @@ function retry_long {
   retry 30 1 "$@"
 }
 
-function echored {
-  tput setaf 1
-  tput bold
-  echo $@
-  tput sgr0
-}
-
-function echogreen {
-  tput setaf 2
-  tput bold
-  echo $@
-  tput sgr0
-}
-
-function echoyellow {
-  tput setaf 3
-  tput bold
-  echo $@
-  tput sgr0
-}
-
-function echoblue {
-  tput setaf 4
-  tput bold
-  echo $@
-  tput sgr0
-}
-
 function is_set {
    # Arguments:
    #   $1 - string value to check its truthiness

test/integration/connect/envoy/run-tests.sh

@@ -354,10 +354,10 @@ function verify {
     $(network_snippet $CLUSTER) \
     $(aws_snippet) \
     bats-verify \
-    --pretty /workdir/${CLUSTER}/bats ; then
+    --formatter tap /workdir/${CLUSTER}/bats ; then
-    echogreen "✓ PASS"
+    echo "✓ PASS"
   else
-    echored "⨯ FAIL"
+    echo "⨯ FAIL"
     res=1
   fi
 
@@ -472,7 +472,7 @@ function run_tests {
 
   # Allow vars.sh to set a reason to skip this test case based on the ENV
   if [ "$SKIP_CASE" != "" ] ; then
-    echoyellow "SKIPPING CASE: $SKIP_CASE"
+    echo "SKIPPING CASE: $SKIP_CASE"
     return 0
   fi