chore: Add 1.7 to release status table in RELEASE_POLICY.md

I forgot about it last week. Note that 1.5.0 is _not_ pushed out of
support by 1.7 since it has not been 6 months since its initial release.

Signed-off-by: Patrick Roy <[email protected]>

Author: roypat

docs/RELEASE_POLICY.md

@@ -90,6 +90,7 @@ v3.1 will be patched since were the last two Firecracker releases and less than
 
 | Release | Release Date | Latest Patch | Min. end of support | Official end of Support         |
 | ------: | -----------: | -----------: | ------------------: | :------------------------------ |
+|    v1.7 |   2024-03-18 |       v1.7.0 |          2024-09-18 | Supported                       |
 |    v1.6 |   2023-12-20 |       v1.6.0 |          2024-06-20 | Supported                       |
 |    v1.5 |   2023-10-09 |       v1.5.1 |          2024-04-09 | Supported                       |
 |    v1.4 |   2023-07-20 |       v1.4.1 |          2024-01-20 | 2024-01-20 (end of 6mo support) |