doc: standardize on End-of-Life capitalization

Use "End-of-Life" everywhere and not "End-of-life" or "End-Of-Life".

PR-URL: https://github.com/nodejs/node/pull/26442
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Anto Aravinth <anto.aravinth.cse@gmail.com>

BUILDING.md

@@ -72,7 +72,7 @@ There are three support tiers:
 For production applications, run Node.js on supported platforms only.
 
 Node.js does not support a platform version if a vendor has expired support
-for it. In other words, Node.js does not support running on End-of-life (EoL)
+for it. In other words, Node.js does not support running on End-of-Life (EoL)
 platforms. This is true regardless of entries in the table below.
 
 | System       | Support type | Version                         | Architectures    | Notes                         |

COLLABORATOR_GUIDE.md

@@ -359,7 +359,7 @@ the three Deprecation levels. Documentation-Only Deprecations may land in a
 minor release. They may not change to a Runtime Deprecation until the next major
 release.
 
-No API can change to End-of-life without going through a Runtime Deprecation
+No API can change to End-of-Life without going through a Runtime Deprecation
 cycle. There is no rule that deprecated code must progress to End-of-Life.
 Documentation-Only and Runtime Deprecations may remain in place for an unlimited
 duration.