[Security Solution] .siem-signals index continuously rolls over if version in template is higher than built in version

[marshallmain]

Kibana version:
7.10

Describe the bug:
If the .siem-signals template is manually upgraded to a version higher than the built in version and also sets mapping._meta.version to a version other than the built in version (SIGNALS_TEMPLATE_VERSION) then we will roll over the .siem-signals index every time an admin visits the detections page. This is due to the !== check here, whereas the template uses < to check if it needs to be upgraded here.
In this situation the template does not get upgraded but it continuously tries to upgrade the index, using the same template repeatedly.
Steps to reproduce:

1. Manually update the .siem-signals template so that version and mappings._meta.version are both greater than the built in SIGNALS_TEMPLATE_VERSION
2. Manually trigger a rollover of the .siem-signals index so it picks up the template changes
3. Observe that the .siem-signals index rolls over again each time you load the detections page

Expected behavior:
Rollover should only occur automatically on loading the detections page if the index version is less than the built in version.