Clean up RelNotes for 2.48

There somehow ended up too many bogus "merge X later to maint"
comments for topics that cannot be merged ever down to 'maint'
because they were forked from more recent integration branches
in the draft release notes.  Remove them, as they are inviting
for mistakes later.

Signed-off-by: Junio C Hamano <[email protected]>

Documentation/RelNotes/2.48.0.txt

@@ -109,21 +109,17 @@ Fixes since v2.47
    (merge 0c1a9987da db/submodule-fetch-with-remote-name-fix later to maint).
 
  * Fixes compile time warnings with 64-bit MSVC.
-   (merge 386d372031 sk/msvc-warnings later to maint).
 
  * Teaches 'shortlog' to explicitly use SHA-1 when operating outside
    of a repository.
-   (merge b33001645e wm/shortlog-hash later to maint).
 
  * Fix 'git grep' regression on macOS by disabling lookahead when
    encountering invalid UTF-8 byte sequences.
-   (merge ce025ae4f6 rs/grep-lookahead later to maint).
 
  * The dumb-http code regressed when the result of re-indexing a pack
    yielded an *.idx file that differs in content from the *.idx file
    it downloaded from the remote. This has been corrected by no longer
    relying on: the *.idx file we got from the remote.
-   (merge 863f2459a2 jk/dumb-http-finalize later to maint).
 
  * When called with '--left-right' and '--use-bitmap-index', 'rev-list'
    will produce output without any left/right markers, which has been
@@ -145,7 +141,6 @@ Fixes since v2.47
    opened at the destination path.
 
  * Other code cleanup, docfix, build fix, etc.
-   (merge 66893a14d0 ps/leakfixes-part-8 later to maint).
    (merge 1164e270b5 jk/output-prefix-cleanup later to maint).
    (merge f36b8cbaef jh/config-unset-doc-fix later to maint).
    (merge 4154ed4108 js/doc-platform-support-link-fix later to maint).
@@ -157,14 +152,4 @@ Fixes since v2.47
    (merge 6dab49b9fb tc/bundle-uri-leakfix later to maint).
    (merge f1ed39987b xx/protocol-v2-doc-markup-fix later to maint).
    (merge 41869f7447 ak/typofixes later to maint).
-   (merge f1eea0b620 ak/typofix later to maint).
    (merge dcd590a39d bf/t-readme-mention-reftable later to maint).
-   (merge 52acf6771b kh/submitting-patches later to maint).
-   (merge a73070fbd4 ks/t4205-fixup later to maint).
-   (merge 9e362dd060 co/t6050-pipefix later to maint).
-   (merge 91687cd13f sk/t7011-cleanup later to maint).
-   (merge 19c291e5b2 ua/t3404-cleanup later to maint).
-   (merge c32d4a8cfe ss/duplicate-typos later to maint).
-   (merge 09bf122507 sk/t9101-cleanup later to maint).
-   (merge c348191afe ak/t1016-cleanup later to maint).
-   (merge f56f9d6c0b ak/more-typofixes later to maint).