[deps] rev markdown and dartdoc

dartdoc:
494a6bed  2023-02-02  Sam Rawlins  Bump markdown dep to a pre-release of 7.0.0 (#3321)
ad6f1612  2023-02-02  Devon Carew  introduce an environmentProvider abstraction (#3324)
d0b73000  2023-02-02  Sam Rawlins  Prepare testing code for some upcoming Warnings (#3322)
936a7888  2023-02-01  Sam Rawlins  Add text about front-end manual testing (#3286)
cbee812d  2023-02-01  Sam Rawlins  Avoid renaming generator params (#3316)
bcaa0349  2023-02-01  Sam Rawlins  Privatize Library.sdkLib and move getClassByName (#3317)
af32def5  2023-01-31  dependabot[bot]  Bump github/codeql-action from 2.1.39 to 2.2.1 (#3313)
528e97da  2023-01-31  dependabot[bot]  Bump actions/cache from 3.2.3 to 3.2.4 (#3312)
54020672  2023-02-01  Parker Lougheed  Begin changelog for next release after 6.1.5 (#3315)

markdown:
f51c24c  2023-02-01  Zhiguang Chen  Prepend a line ending if the p tag is removed and there is an element before it in a *tight* list (#513)
dd3e3a1  2023-01-31  dependabot[bot]  Bump dart-lang/setup-dart from 1.3 to 1.4 (#510)
5f25fc9  2023-01-31  dependabot[bot]  Bump actions/checkout from 3.2.0 to 3.3.0 (#511)
54266b2  2023-01-31  Kevin Moore  Prepare to release v7.0.0 (#509)
d6ceff9  2023-01-31  Zhiguang Chen  Add line endings before HTML blocks (#508)
ccd3c8b  2023-01-29  Zhiguang Chen  Rewrite link reference definitions (#506)
e8f84dc  2023-01-24  Kevin Moore  Update GFM to 0.29.0.gfm.7 (#507)
93f67b0  2023-01-20  Zhiguang Chen  Add an `enableTagfilter` option to `HtmlRenderer` to eanble GFM `tagfilter` extension (#447)
d110770  2023-01-13  Zhiguang Chen  Rewrite SetextHeaderSyntax (#500)
c1b9bc6  2023-01-09  Sam Rawlins  Migrate from no-implicit-casts to strict-casts (#504)
3e78c08  2023-01-01  dependabot[bot]  Bump actions/checkout from 3.0.2 to 3.2.0 (#501)
417747f  2022-12-15  Zhiguang Chen  Refactor list syntax (#499)
30ec05f  2022-11-29  Zhiguang Chen  Do not escape single quote(apostrophe) inside code (#498)
c3d1136  2022-11-29  Zhiguang Chen  introduce a Line class (#494)
Change-Id: I9d971b927b72500ab84cce461a60fe1a86818e2e
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/281543
Reviewed-by: Samuel Rawlins <srawlins@google.com>
Commit-Queue: Devon Carew <devoncarew@google.com>

Author: devoncarew

DEPS

@@ -135,7 +135,7 @@ vars = {
   #
   # For more details, see https://github.com/dart-lang/sdk/issues/30164.
   "dart_style_rev": "d0c6b1da52c9f80679a7aaa05e5935ef5c6bb52f", # manually rev'd
-  "dartdoc_rev": "bc7bdc44b03c558c9993f178d19ad989ed1c5f12", # https://github.com/dart-lang/markdown/pull/494
+  "dartdoc_rev": "494a6bed4992ea4ee1d831e6bcf20ab645da950b",
   "ffi_rev": "69d759613f9be3a897ce9a67910e9914694c96f3",
   "file_rev": "72a67c33f90bfb7e10057e286e06d2fe3baa4d98",
   "fixnum_rev": "f8379d94436f3a73f71ea078f3207897c6700498",
@@ -149,7 +149,7 @@ vars = {
   "linter_rev": "70fb087e39e6882ad331ee1e3f52f3f3a88e2d16", # 1.33.0 (+ `unnecessary_parenthesis` fix)
   "lints_rev": "dfded5e265015f21ce154577fe8488dc244e33c2",
   "logging_rev": "abef3717d958158eb8b0ddb2871f4b15a9804cd4",
-  "markdown_rev": "ee3f4e976efcfed87c6ec78364bc2dd3c6e717b9", # https://github.com/dart-lang/markdown/pull/494
+  "markdown_rev": "f51c24c5c5603ac20b6d88aded78ef3aa23619ac",
   "matcher_rev": "c1a07043de3da4968e1736fcde1c521802821859",
   "mime_rev": "1a51be02b3cbc742c79d83575bd096ae8c295c1f",
   "mockito_rev": "d2a8df169706d1c1e5daaf0c96ee03b8238bd599",