fix(apps/prod/tekton/configs/tasks): fix clone-ext for hotfix cases

before:
```
~/tidb # MAJOR_MINOR_PATCH=$(echo "$RELEASE_VERSION" | awk -F. '{print $1 "." $2 "." $3}')
~/tidb # echo $MAJOR_MINOR_PATCH
v7.5.2-20240705-eaff0fb
```

after:
```
~/tidb #  MAJOR_MINOR_PATCH=$(echo "$RELEASE_VERSION" |grep -oE "^v[0-9]+[.][0-9]+[.][0-9]+")
~/tidb # echo $MAJOR_MINOR_PATCH
v7.5.2
```

Signed-off-by: wuhuizuo <[email protected]>

apps/prod/tekton/configs/tasks/pingcap-git-clone-ext.yaml

@@ -133,7 +133,7 @@ spec:
           EXT_REVERSION=$(echo "$MAJOR_MINOR" | sed -E 's/^v/release-/')
         elif [[ $origin_ref =~ "^release-[0-9]+\.[0-9]+-.*-v[0-9]+\.[0-9]+\.[0-9]+" ]]; then
           # hotfix branches
-          MAJOR_MINOR_PATCH=$(echo "$RELEASE_VERSION" | awk -F. '{print $1 "." $2 "." $3}')
+          MAJOR_MINOR_PATCH=$(echo "$RELEASE_VERSION" | grep -oE "^v[0-9]+[.][0-9]+[.][0-9]+")
           EXT_REVERSION=$(echo "$MAJOR_MINOR_PATCH" | sed -E 's/^v/release-/')
         elif [[ $origin_ref =~ "^(master|main|feature/.*)$" ]]; then
           EXT_REVERSION="master"