Enable markdownlint no-trailing-punctuation and no-blanks-blockquote (#29214)

Enable these two and fix issues.

.markdownlint.yaml

@@ -5,13 +5,11 @@ heading-increment: false
 line-length: {code_blocks: false, tables: false, stern: true, line_length: -1}
 no-alt-text: false
 no-bare-urls: false
-no-blanks-blockquote: false
 no-emphasis-as-heading: false
 no-empty-links: false
 no-hard-tabs: {code_blocks: false}
 no-inline-html: false
 no-space-in-code: false
 no-space-in-emphasis: false
-no-trailing-punctuation: false
 no-trailing-spaces: {br_spaces: 0}
 single-h1: false