Fix broken links in security section

Linkcheck encountered issues with some links. In two instances it was a
simple 404 issue with a changed location of content. In the other the
link functions in the browser, however linkcheck seemed to have issue
with GitHub links linking to specific line numbers.

For the link in `cert-rotation.rst`, it was simply removed, as it did
not feel necessary.

QA Steps: ran linkcheck

No related issues/tickets, minor quick fix.

Signed-off-by: Katrina Prosise <katrina.prosise@foundries.io>

source/reference-manual/security/cert-rotation.rst

@@ -47,14 +47,11 @@ The certificate renewal logic uses the EST 7030 `simple re-enrollment`_ process
 
  * EST Server verifies request, creates a new certificate, and returns it to the device
 
- * The new certificate is valid for `one year`_
+ * The new certificate is valid for one year
 
 .. _simple re-enrollment:
    https://www.rfc-editor.org/rfc/rfc7030.html#section-4.2.2
 
-.. _one year:
-   https://github.com/foundriesio/estserver/blob/1b32b40729c60e8dfa21155dd1d31135244e56c1/service.go#L210
-
 Tracking Progress
 -----------------
 

source/reference-manual/security/imx-generic-custom-keys.rst

@@ -101,4 +101,4 @@ close the board, respectively.
   after understanding its critical implications.
 
 .. _i.MX Secure Boot on HABv4 Supported Devices: https://www.nxp.com/webapp/Download?colCode=AN4581&location=null
-.. _Generating a fast authentication PKI tree: https://github.com/nxp-imx/uboot-imx/blob/lf_v2022.04/doc/imx/habv4/introduction_habv4.txt#L193
+.. _Generating a fast authentication PKI tree: https://github.com/nxp-imx/uboot-imx/blob/lf_v2022.04/doc/imx/habv4/introduction_habv4.txt

source/reference-manual/security/secure-boot-uefi.rst

@@ -82,7 +82,7 @@ Once PK is added by the user, most UEFI implementations move the active mode fro
 Creating UEFI Secure Boot Keys
 -----------------------------------
 
-The suggested way to create a custom set of UEFI Secure Boot keys and certificates is via the `lmp-tools gen_uefi_certs.sh <https://github.com/foundriesio/lmp-tools/blob/main/security/uefi/gen_uefi_certs.sh>`_ script.
+The suggested way to create a custom set of UEFI Secure Boot keys and certificates is via the `lmp-tools gen_uefi_certs.sh <https://github.com/foundriesio/lmp-tools/blob/master/security/uefi/gen_uefi_certs.sh>`_ script.
 
 1. Clone the ``lmp-tools`` repository from GitHub